There were so many expensive TV shows being made that it simply wasn't sustainable.

We're actually back to normal. TV before streaming was A LOT of reruns, trashy talkshows/reality TV, soaps and quiz shows.

The 90s and earlier, yeah. But cable in the first 15 years of the 2000s is where TV peaked quality-wise. Streaming captured the max output, but peak TV quality was largely before streaming went from re-runs to new-production. The 2015-2022 era honestly watered the quality down quite a bit.

IMDB Top shows ratings https://www.imdb.com/chart/toptv/ - the bulk of the top for scripted series are cable shows (especially HBO)

RottenTomatoes fan picks https://editorial.rottentomatoes.com/guide/rt25-fans-top-tv-... - very similar list