Team fortress 2 has changed in many ways in the 6 years I've played, and is slowly moving downhill to what will be its end.

Scout.
Scout is the fastest moving class, can double jump, and has possibly one of the most Overpowered weapons in the entire game. The scattergun. When I first starting playing, the scout was barely used for direct combat and would normally avoid enemies by jumping or simply running around. Capturing control points, the inteligence briefcase, simple distraction, all the things the scout was meant to be. Now going through to today, most play scout as a direct combat class. I know I'm not the only one when I say I've seen scouts use the sandman to stun, then run up to their target and shoot. This never happened 5 years ago. Today, as in the 4th of July, 2014, scouts are now the overpowered and unbalanced class that is used for fighting.

Soldier.
The soldier is a powerful offencive and defencive class, and Is also a great beginer's class to learn the game with. When I first started playing, the soldier was right on the front lines along with other offencive classes, destroying sentry guns and pinning other players down, or simply destroying enemies. The soldier is one of the few classes that hasn't changed much. Still used as a front line breaker and overall good class, though I have seen some using the new B.A.S.E. jumper, rocket jumper, and market gardener to be more of a support class that isn't set up for direct combat. I have nothing against this but it is important that all soldiers know their role if needed.

Pyro.
The pyro is the well, pyro. Pyro uses a flamethrower to burn enemies, amubush, and even use corners to destroy buildings. Years ago the pro was strictly the ambush offencive class and would wait around corners while advancing to the objective. Now, as of today, the pyro as undergone change just like the scout. More and more pyros now W+M1, or use their flamethrower while charging an enemy. This will kill most classes within seconds at most, but is rather overpowered. Perhaps that is their goal, or maybe they're just looking for an easy way to play. The other pyro flaw is the degreaser. Sure it has reduced damage and afterburn, but is mainly used with the flare gun or reserve shooter and axtinguisher or other melee. From what I've seen, the pyro will ignite their target with the degreaser or flaregun, and will either airblast with the degreaser then shoot with the reserve shooter, or flare gun. This grants critical or mini-critical hits. The axtinguisher has recently been "Nerfed" To minicrits against burning targets instead of full powered critical hits. Even minicrits can make a big difference.

Demoman.
The demoman is an expert in explosive weapons and can be perfect with ambushes using the stickybomb launcher. Years ago (sorry for repeating but I need to get the point across) demomen would normally lay sticky traps on control points, the intel briefcase, or even walls to ambush their target. The grenade launcher is good for shooting around corners and even up to destroy sentries on a higher level. Today, demomen still practice stickybomb and grenade launcher ambushes and destruction, but a new style of demoman has come forth. The demoknight. I'm not saying demoknights didn't exist years ago, they just weren't commonly used. Now demoknights can be seen in almost every server. Sure, a demoknight is good for scrambling targets for an assault squad, but they rather go and just kill on their own. I'm not saying I didn't commit this crime, but demoknights have almost ran all stickybomb demomen out of existance.

Heavy.
The heavy has the most HP and uses a minigun. Heavies are labeled defence, but can be found on offence just as often. Their minigun is a high-powered, close range weapon that is able to kill targets in under a second at the right range. When I first played, the heavy wasn't used as often but when he was, the heavy was on defence and would be right next to the engi and his sentry, or would have a medic at his back to push the enemy's front lines back. Today the heavy is used as an offencive and defencive class just as much, but heavies with a medic at their back can mop the floors with anything, and require teamwork to take down. The heavy has stayed nearly the same, but is more offencive now.

Engineer.
The engineer is a perfect defence class, they have the ability to build sentry guns, dispencers, and teleporters. The sentry is a high powered defencive tool that is perfect for putting near the control point of some defencable object. The dispencer can supply ammo and health to teammates, while the teleporter can quickly move teammates to the front lines. Engineer hasn't undergone too much change, but enough to make it somewhat annoying. The widowmaker is a shotgun used by the engineer and can easily go for many shots before requiring ammo, which can make it annoying as all hell when they keep shooting and shooting and shooting. The gunslinger is another weapon that has made the engi less enjoyable. They give the wearer +25 HP and replaces the full-sized sentry with a minisentry, a smaller version that seems to have longer range and almost the same power as a tier 2 full-sized sentry. The minisentry can be found used more of a offencive tool than defencive, and is just one of those things that can be found annoying.

Medic.
The medic is the team healer and is the only class able to regenerate health with no special tool or weapon. Almost half the medics out there have gone from healers, to fighters. Weapons such as the Blutsauger are commonly used just to fight. I'm not saying I haven't done this, but when a medic sticks to a heavy or doesn't heal at all, don't you think they're just kinda useless? I've had medics run right past me after I call for a medic, just to go and shoot at some enemy, instead of doing their original job of healing. Now if a battlemedic heals as well as fights, that is different, but a medic with a quick fix will most likely just heal until their teammate is full health and then will continue their killing spree.

Sniper.
The sniper is a support class that can kill every class with a well placed, full charged sniper rifle headshot, or a fully drawn bow headshot. Now sniper has changed quite a bit, they've gone from a rifle using crazed gunman who can drop high value targets from a difference, but when using a bow, their range is shortened. I'm not saying the bow is bad, it's great, what I'm building to, is the SMG snipers or the no-scope snipers. There are snipers that will take their time to run after targets using only the SMG, and is quite a weak while doing so. The SMG is the close ranged defence weapon when a target gets too close for a bow or rifle shot. Now the no-scope snipers really do piss me off, since they're so useless. There are a few times when a no-scope shot is needed, say the sniper has something else instead of a SMG as secondary, and the target is just out of reach of melee. Just today I saw a sniper using the heatmaker on 2Fort, so what, big deal right? This sniper wasn't using a scope though. He was shooting across the bridge to the enemy's battlements with no scope, and was just firing blindly. This happens way too often.

Spy.
The spy is a major support class that can sap engineer's buildings, and backstab targets to weaken the team for the assault to move in and wipe out the rest. Now as of today, spies don't sap as much and mainly run around. Instead of getting behind enemy lines to backstab, they charge right in. Smart, right? No. Spies have gone from stealth classes that can instantly kill a target with a backstab, to spies who "Facestab" and fight with the knife as a melee, and then there are battle spies who use their revolver more than their knife.

So with everything about Team Fortress 2 changing majorly, or slightly, it will never be quite as fun as it was when it first came out.