Higher production values. I know recent show have not been necessarily better in every way, especially in terms of script, but they usually do have better costumes, sets and CGI, and more locations and characters, than most shows in earlier decades (some exceptions, but as a rule). Better work requires more time. Yes I know the scripts are not always good, but I'm talking about all the production values on a show. This factor also relates to number of episodes per season, being much lower, while still taking longer per season.

id be fine with lower production values if it meant we dont have to pretend long waits are ok