I'm biased because I grew up with Spongebob. I actually saw the series premiere live on TV (Same with South Park). So it's hard to divorce myself from the show without a nostalgic bias. I also haven't re-visited it. That said, I think most people say that Spongebob was great for the first couple of seasons and died with the movie?
After the movie, it's fair to say it died.
Even as a kid you just kinda know it's not the same.
Yeah after the movie it was never the same as Stephen Hillenburg wanted to end the show after the movie but Nick wanted more episodes so he resigned as showrunner for the show and since then it's being all downhill in terms of quality.