The answer to the question is subjective as some people find the Spongebob show bad from the start or it is still great up to this day. But in my opinion, I like the older episodes (seasons 1-4) when Stephen Hillenburg was part of the show compared to the newer ones. The first 4 seasons have great jokes even in the smallest scenes. Aside from jokes, there are numerous quotes that people can relate to or learn from.
Maybe the Spongebob new team is adjusting when the creator and other crew members left thus resulting to lesser quality episodes. This change or decline is noticed mostly by die-hard Spongebob fans.