I have an integrated bar (PRO Stealth Evo) on my newest road bike. I like it fine. It replaced a FSA integrated bar that was on the bike when I bought it because the dimensions weren't right for me. I have separate pieces on my gravel bike and MTB. I would put an integrated on my MTB without hesitation. I REALLY love the bar that I have on my gravel bike right now, and don't want to give that up.

An argument can certainly be made that an integrated bar's lack of rotational adjustability is a step backwards.