On the topic of crutches, I like to think of it this way: against someone using the stock loadout for a class, would this weapon or weapon combo regularly win out?
In the case of the Liberty Launcher, think of 2 equally-skilled Soldiers standing relatively close to one another. In an average fight, the player using the stock launcher has an extra rocket, but the Liberty Launcher's rockets travel much faster, meaning the LL Soldier gets their hits in faster. Plus, the 4th rocket doesn't even come into play because at close to medium range, where the LL shines, 3 rockets will usually kill everything but a Heavy.
With the Tomislav alone, the nerf it got the day after the Uber Update was sufficient. When it first came out, a Tomislav Heavy at close-medium range would decimate any other Heavy. The nerf made it so that Minigun Heavies could prevail (but with about 5-10% HP left). The problem with that is, while it's balanced against other Minigun Heavies, at the same time, it completely outstrips the Brass Beast and Natascha, with their slow spin-up times. In fact, a Tomislav Heavy can spin up and kill either before they get a chance to fire one bullet. The weapon also removes a core weakness; namely, the spin-up time associated with his primary weapon. This really unbalances it against every other class; instead of being able to get a couple hits in and escape, there suddenly is no escape; within half a second, that Heavy is now firing on you, doing 400+ DPS at close range.
Now, imagine a Heavy using the Tomislav, Sandvich, and GRU in combat, compared to a Heavy using the stock loadout. The stock Heavy moves very slowly, cannot heal himself, and has to be careful about picking his battles, because the spin-up time of the Minigun means he could take heavy damage before even being able to do any damage of his own. The Heavy using unlocks can run at 100% speed, losing piddling amounts of health along the way, drop his Sandvich for instant healing of up to 150 damage, and jump into battle without having to be mindful of his spin-up time, because there practically isn't one. It teaches Heavies that they don't have to watch their health or mitigate their spin-up time to do huge amounts of damage.
Now, the Enforcer. Once again, in a stock situation, you'll handily kill the stock Spy before he kills you. No matter what he does, in a situation where crits are irrelevant, he cannot kill you in 2 shots from full health. You can be at mid-range and still 2-shot him. Another good way to compare it is against a Scout; you can actually 2-shot a Scout before he can get 2 meatshots on you, and you can do it from mid-range, where his Scattergun is less effective. Against a Soldier, if you get the first hit in, he won't have time to even fire 2 rockets before you kill him with 3 shots. Probably the biggest offender is against the Pyro; with the Enforcer, you can 3-shot a Pyro outside the range of the Flamethrower, which is something that would take the revolver at least 4 shots to do. It doesn't seem like much, but it changes dynamics of the match-ups between different classes dramatically. Even with the IW/CnD, the Enforcer's downside is very negliable; it takes a bit of getting used to, but it's not much of a downside. With the Dead Ringer, however, not only can you 2-shot light classes, but you essentially have an "oh shit, give me 10 times my current health for 6.5 seconds!" button that can be easily charged by picking up ammo. The 2 together is a crutch, in the sense that it turns you into a (not-so) glass cannon, as opposed to a sneaky, backstabbing bastard. It allows players who are effing terrible at the class to play it and win in fights they should not ever have a chance of winning. This reinforces so much bad behavior, just like TomiGRUvich; instead of sneaking around, going for key picks against important classes, they walk out onto the battlefield guns blazing, and if they take any damage, they immediately DR through it, decloak, and continue shooting.
Finally, the Spy-cicle. In this case, the stock vs. unlock example doesn't work, but instead we have to look at it objectively, and how people typically use it in combination with other weapons. Probably the most prominent effect on the knife is the silent backstabs (bear with me here). It's very similar to the YER, except with that knife, you have to get an initial stab to not be walking around exposed; the Spy-cicle allows you that luxury. Setting up a chain-stab is very difficult against experienced players, as players let out a very distinctive scream when they die to a backstab. The Spy-cicle eliminates this downside by making each kill nearly silent. The only sound the weapon makes on a backstab is a faint crackling sound that is barely audible; in fact, the crackling is quieter than the decloak sound of the IW or CnD. So, in a sense, it has a major advantage over both the stock Knife and YER, when it comes to that. But that's not really a crutch, that's an advantage. The crutch of the weapon is the fire immunity; Pyro is arguably the hardest counter a Spy has, and negating that counter, even for 2 seconds, is just bad design, especially given the other unlocks.
Let's pit a Dr. Enforcicle Spy against the stock Spy. The only utility the stock loadout has is the fact that they can cloak on demand; it is outclassed in every single other way. The Enforcer deals more damage, the Spy-cicle has silent backstabs and can be sacrificed for fire immunity, and the Dead Ringer gives you 6.5 seconds of immunity from everything save environmental hazards and repeated backstabs. Together, they are effing formidable; Scout or Soldier in your face? Shoot them to death. You can't hit them enough to get the kill? DR out of it. A Pyro comes along? You can either shoot him with the Enforcer, or DR out of it, then use the Spy-cicle to cover your tracks long enough to escape. When you uncloak, you still have a gun powerful enough to deal with all but a Heavy easily. If you choose to stay and fight the Pyro, you can shoot them once, use the Spy-cicle for immunity, then shoot them twice more while immune. And if all else fails, after all that, you can just DR out of it and walk towards your teammates, who will most likely shoot the Pyro.
The point I've tried to make with this is, there are crutches is the game, and Kaitostrike has a point; they lower the skill floor and skill ceiling. A very good Soldier would easily do more damage with that 4th rocket, or perhaps even use the Direct Hit for maximum damage plus the airborne minicrit functionality. A very good Heavy (sorry, lol) would be able mitigate his slow spin-up time with the Minigun in a variety of ways for that extra bit of damage. A very good Spy doesn't need all the advantages Dr. Enforcicle brings to the table because he knows how to divert attention, shift paranoia, and use his cloak to its maximum effectiveness; hell, I did it enough with the L'Etranger and Kunai to rack up 700+ and 8500+ kills, respectively.
And that's just using the examples that were listed; there are a few other weapons that are equally as bad.
