[n_plus_1_acc]

Many indie games use Unity and have terrible performance. Source: I have a potato (by which i mean i use the integrated graphics of an i7-56xx)

It can run many games well, so it depends how much developers value performance.

[barbecue_sauce]

As a player, I do not really value performance unless we're talking sub 25fps.

[account42]

Performance is not just a simple number. 25 FPS with good frame pacing is much more enjoyable than something that averages 60 FPS but with individual frame times all over the place. That said, for first-person action games especially on a non-tiny monitor, anything below ~40 FPS will be noticeably non-smooth. Other game types have more tolerance, e.g. a top down strategy game could still be playable at ~15 FPS.

[n_plus_1_acc]

Same. But some titles have like 3fps (Train Valley World for example)