People say that about every show, and if I had to take a guess people have said that about South Park probably as early as Season 2-3. Creators change and age, and so the audience. Sometimes this aligns well, sometimes it doesn’t. I personally think South Park is still funny (there are some hits and some misses), but the reality is it’ll always be changing.
For me 19 was solid, 20 was interesting but they got screwed banking too much on the elections + trying to do a 7 days to air style with a running plotline. The tegridy seasons weren’t my cup of tea. I personally liked the more serious specials like COVID that were more narrative based than comedy based, it struck a nerve for me.