func_breakables players can destroy are generally seen as fine as long as they're either just details or you're mapping for a mode where frequent map resets happen (i.e. Arena).
And I may be in the minority here but I always found the breakable tunnel wall at 2nd of cp_warpath to be fun.
Perhaps I'm part of the same minority. The breakable tunnel in warpath was definitely fun.
If used correctly, it could easily change a stalemate on 2nd and 3rd to a push from 2nd to 1st, provided the enemy team's defenses weren't up to par to repel the attack. But it was only good once, so you had to make it count or it was pretty much open season for the opposing team (unless the first wall wasn't broken, in which case it was all good).
Ah... now I wish to play that map again, lol.
EDIT: To keep on track with the thread, I don't believe there is a reason you need to avoid it, provided it is used correctly or in a way that isn't too detrimental to the game (kinda like on warpath). Just make sure your players know, or at least make it really obvious, that the walls in question can be broken, or they may not figure it out.
Like others have said, it is only good once per map, so a map change will be needed to reset it. I'm sure too many of them may impact performance, but a couple here or there doesn't hurt anything.