I think with the success of streaming series have become more interesting to streaming platforms as their addictive nature can lock people more easily into a platform for a specific period of time.
For this reason budget and revenues of series have increased dramatically and series are more and more produced like movies. This probably created an artistic and talent shift from movies to series.
There were a lot of shitty movies too back in the days but some never even reached the theaters and were only sold on VHS and DVDs.
Movies have historically been stand alone - if you didn't see [random movie]-1 when it was out but now your friends want to go to [random movie]-2 the movie better make sense. However it can still clearly be a follow on. As such movies tend to focus on a plot within the movie.
TV shows have been more a case of you may have missed yesterdays show, but want to see today's show. The format doesn't lend to complex plots because of the limited time to resolve them, and anything long term means people are seeing spoilers. Thus they tend to focus on characters, so you can watch in more or less any order.
For this reason budget and revenues of series have increased dramatically and series are more and more produced like movies. This probably created an artistic and talent shift from movies to series.
There were a lot of shitty movies too back in the days but some never even reached the theaters and were only sold on VHS and DVDs.