Generally speaking, if your single mic IR is great, it's because it's an IR you've miced yourself
It's not the quality of the single mic IRs that's in question, it's the banality and overuse of them. You can pretend that you've reinvented the wheel by using whatever big brand 57/V30 IR, but you're just outing yourself as a beginner most of the time.
This is why everyone complains about YouTuber tones.
Multiple mic setups aren't the ONLY use for IRs, they're just a great use-case because it's much simpler than an IRL multi-mic setup.