So, I've finally got to play and finish this game. All Achievements and 100% monster collection (didn't bother to get all medals and accessories though). Now here's my 2 cents about the experience:

Story:
The story is... there. If you've played DQ4, you will have some "fun" moments with this game. If not, then the story is mainly there to give you a reason to go to places. Occasionally it WILL feel like you're missing some context for Psaro's actions, so if you've heavily invested in the story of your games, this is not the game for you.

Gameplay:
I will seperate the gameplay from the breeding/collection aspect and battle, so keep that in mind.
The gameplay itself is fine. Psaro controls nicely on the map, I think he's neither too slow nor too fat movementwise, although sometimes I would have wished for something like a vehicle mid-game. The gameplay is what you'd expect form a monsters game. You run around on a world map and see monsters there. If you touch them, you engage in battle. A part I wish they would have done better though is, that if you sneak up on them, I'd have appreciated a surprise attack to be performed. As of writing this, regardless of how the battle starts, it's random if the enemy snuck up on you, or you on them, it's completly random. Other than that, you run around different worlds and have multiple set markers where you can easily teleport to, which is a GREAT feature for easy travel. This game also has a 4 seasons mechanic, which as the name implies changes the seasons every few minutes (or with an item) which then changes some of the monster spawns as well as some locations, making them accessable.

Battle:
You have a party and a backup party with up to 4 monsters each, each monster can wear 1 accessory and you can either Order your monsters to do certain actions, or just press "GO" and your monsters will do stuff based on which tactics you've employed for each monster. A nice added feature compared to older games is, that you can tell your monsters which skills to use how often. Eitehr high frequency, low frequency or not at all. So for instance a healer who has some attacking skills as well can be tinkered with and set to ONLY use healing spells. But once your party hits a certain power treshhold, you will be mostly using the auto battle feature. Even the secret boss, who was no doubt the hardest boss in the game was killed without me giving orders directly. I only used party healing items and MP healing items when my healer was getting low on MP and then it just became a game of resources and patience.

Breeding and monster collection:
Since this is a MONSTERS game, the breeding and collection is a major part. This has been made pretty easy, if not too easy with the DLC. First the general mechanics: Unlike older games, where you had to have a male and a female monster, this game is genderless, meaning that every monster can breed with any other monster, as long as they are both level 10+. This makes it SO MUCH LESS ANNOYING than older games, where you'd have more often than not the right monsters, but both be male or female and therefore unbreedable. The game also has a great feature called "reverse search" which let's you specify what kind of monsters you want to create like family and rank. But the most helpful part in the search is, that it can show you ALL monsters you haven't had yet and how to get them by the press of 2 buttons. Really great quality of life change compared to older titles. I played the game for roughly 100hours (no guide till I beat the secret boss) and sinihed around 85% of the monster collection just by playing the game. Only certain monsters require a guide to get, but for the most part you will be fine, if you just keep your storage full with different monsters at all times.

Postgame:
Sadly therer isn't much contentwise. You get a full new zone, where you can fight 5 more special boss battles, a flute to change the seasons whenever you want, 2 S-rank tournaments and once you beat the secret boss a drastically improved Metal Sllime King spawnrate. That's it. After that you can go for completion and achievement hunting, but it's neither required nor additional content.

Soundtrack:
It's great, what can I say. This is the soundtrack I've grown up with almost 30 years ago and it still holds up. Nowadays it's obviously not an 8-Bit version anymore, but these tracks are so chill, you can easily listen to them for hours while gaming.

DLC:
Now this is where I'm conflicted. Once you hit a rather early part of the story, you will unlock the Paddock and in there 3 DLC NPCs. Those will give you a treasure every hour, multiple dungeons with certain requirements (rank or family) and interesting item rewards and finally the Mole Hole, which are a couple of dungeons with different ranks, where ONLY monsters you've already owned appear.
-) The treasure: It's fine. If you care for free loot and remember to get it, you can certainly go there every hour, but it's no major game changer.
-) The dungeon: Now this is an interesting part and maybe even the true "postgame challenge" to complete. You can find monsters here that you usually have to synth for, exp items that will help you grind your monsters up later on and some good accessories as dungeon clearing rewards. I mostly used it early game to get some levels in and monsters that I didn't have, but stopped using is after realising it's DLC, cause it made me feel like I was cheating.
-) The Mole Hole. THIS is NO DOUBT the best DLC in the game. This will make your monster collection journey go from 200h to 50h. Having a relatively easy access to ALL monster species you've owned before is a godsent. Some A&S rank monsters, which are quite hard to synth are required multiple times (like Aamon), but with this, you literally need to get every monster once and you'll have an infinite amount of copies available (if you can catch them). This helped a lot during midgame, where I got my first B rank monster (Mohawker) and used it like 30 times as a base to synth other B Rank monsters and increase my overall party strength by A LOT.

Now for things that I personally didn't like:
-) The puzzles. Now hear me out first. There aren't any unsolvable difficult puzzles, but they are hella annoying. That water puzzle easily took over half an hour, simply because you have to run up and down like 50 times to change the waterlevels properly. It's not hard, it's not challenging, it's just a chore.
-) Egg monsters only. Now if you don't want a certain monster of collection completion, this will not be an issue for you, but after a certain point in the story, you can find eggs on the worldmap, which are generated once you access that area (so no save scumming before opening them directly). When you collect an egg, it will become either a white, silver, gold or rainbow egg and have a monster with an accoring rarity in it. The issue here is, that there are some monsters, that can ONLY be aquired like this and ABSOLUTELY needed to finish the high level monster synth. The biggest offender to me was the "Marques de Leon", which is a high rank beast monster that can ONLY be aquired by a rainbow egg. There are 13 rainbow monsters in total. So not only do you have to get a 1/4 chance to find a rainbow egg, you also have to win the 1/13 chance of getting the RIGHT egg. This was just frustrating and not fun.
-) empty towns, NPCs and side content. So besides the raising of monsters and continuing the story, there really isn't much to do in this game. No NPC battles (besides the tournaments), no trading and like 6 or so NPCs who will synth their monster with yours no side quests and almost no extra bosses.

My verdict:
It's a fine game and if you like the DQ franchise and/or monster catching games, you will have a good time with this. It definitely has it's flaws, but for that price (40€, or 25€ on sale) you will get your enjoyment out of it

Overall if I had to put a number on it, solid 7/10

i would give up my reproductive organs for my monsters.

If you like pokemon you will love it, its like a more mature, smart and funny pokemon.
The story is a bit childish still, but still better than pokemon as well.