This game is just plain fun in every aspect.

guns are balanced very well so in the end your loadout is up to personal preference and metas are just a loose suggestion.
classes are very balanced and each class is useful for a specific purpouse so none of them can be ignored.
the gameplay loop is fun, the ping system with the laser pointer works like a charm, positive interaction between players is encouraged in subtle ways and it resulted in the development of the most friendly community I know.
The lobby has enough side activities that you don't get bored while waiting for the host to start the game, there are 5 levels of difficulty for any level of skill and choosing a lower difficulty doesn't prevent you from unlocking stuff.
Progression sistem is grindy enough to keep you engaged but rewarding enough that you don't get bored, all DLCs are just cosmetic, I incountered a bug just once and then it just fixed itself on its own in the span of 5 seconds.

I can't find a single negative to this game, It feels like the devs though about what are the features that gamers hate and then straight up avoided implementing them. It does what is supposed to do flawlessly.

This game is good, "old valve games" good. Buy it on sale, buy it full price, just buy It.