Only because you're reading the damning into it. Acceptable isn't a euphemism for bad, I just reserve "great" for things that are, well, great. Like Factorio level's of optimization (Even though that game is capped at 60fps). 100+ fps with 7 year old hardware is perfectly adequate in my book. Skimming some popular games that use Unity and run fine: Rimworld, Outer Wilds, Gunfire Reborn, Enter The Gundeon, Risk of Rain 2, Hollow Knight. I see some more, but I haven't personally played or watch someone play them so I hesitate to list them.