It's very hard to approach an explanation on why the slow progress, quite honestly it can also range into other mediums such as music and video games. TV productions not so much due to recent low costs in digital equipment (A complete Arri pickup can grabbed with 150k and a heavy duty drone can replace complex setups and vehicle rentals)
I wouldn't dare to explain why without sounding simplistic it all went to pieces in terms of discipline and management, in both creator and consumer sides
but it is interesting to think how few things are done in ideological groups (other than niche social movements) there has been good films but i feel it's been isolated cases of level-headed, sometimes overachieving workers than true mavericks experimenting with their craft while also making something in terms of storytelling.
I can definitely buy "consumer's drastic change of habits" as a factor if we think about most people using digital services that are very quick but quite limited in selection of works, but i don't know, there must be something else, i can't buy economic crisis and politic mishaps as many countries produced good stuff in times of dire conditions (Post-WWII and early 90's Japan, 80's and early 90's Yugoslavia)
At least in the West i feel a lack of big time investments into specialty/"give this man a chance" projects, it seems suits go for safe bets only and the eccentric millionaires ala Aurelio De Laurentiis seem to be working on other things unrelated, or also cinema but with mixed results and/or highly overlooked.