Yes but: as a player, if I don't agree with the balance concern I'd be a lot less enthusiastic about the game. No class in 5e is overpowered, and I'm not worried about any official subclass offhand. If we're playing 3.5 there's several options that I would agree are too powerful - or so underpowered that you'd rather the player refluff a better class to make the concept work (ie don't play a samurai - play a warblade with pseudo-Japanese fluff). If I don't know the game I'd probably roll with whatever the dm thinks.
It all comes back to a more basic premise in my mind: I don't judge restrictions in themselves; I judge the reasoning behid the restriction.
For example, if your setting just does not have anything even kind of like steampunk in it, you might remove artificers as a class. If that's because you want a really low magic setting that's one thing - but if it's just a low-tech setting I might really want to make a swordmage using the battlesmith mechanics and the rune knight fluff, which could work with nary a cog at all. I'd expect a reasonable hearing-out of the idea, at least.
Honestly the only way you can dm "wrong" is to not let the players pitch stuff at all. What you exclude is just playstyle.