Others are upset because, as the Constitution is written, he cannot force a private website to carry his speech (the Supreme Court has repeatedly rejected “compelled speech”). Although, yes, we should wait for the courts to (hopefully) strike it down.
There’s also the fact that repealing Section 230 would be absolutely detrimental to the internet. Sure, decentralize it all, but, as it stands now, that’s not what the majority of the public want; They want centralization because it makes things easier. Facebook, Twitter, Google/YouTube, etc. are the size they are today because they’re centralized; it makes finding what you want easier.