Well you’ve come up with 2 examples of stop gaps now.
If we can give an older player that’s captained an English champion winning team, vastly experienced and was considered to be one the finest midfielders of his generation, then I’m all for it.
At the other end of the scale there’s Arthur, Kabak, Caulker, etc where all stop-gaps that were a waste of time.
Thiago was also arguably a stop gap.
So in answer to your question… no problem with a stop gap if they offer something significantly important to the team, or they’re good enough to hold down and excel as part of the team… otherwise the question is why? Would we not be as well using a youth player?