building a brand is largely about packaging, and scenes are nothing if not packaging. they take somewhat overlapping but sometimes disparate artists under an umbrella and make it easier for music (or art or writing) fans to identify and explore.
there's just too much competition out there for many artists to be heard without some form of scenes, you'd have a bandcamp world where 10,000+ artists exist but you have no signposts for where to look. I'm sure I've found some great things I'd never hear otherwise if I didn't know the artist was a kindred spirit with another artist I like, etc.
as you say, there's positive and negative, but scenes can be very helpful in navigating. not everyone has the time or energy to explore an unmapped world. the good part is you can ignore scenes if you want, pretend they don't exist and try to wade through on your own. everyone wins!