IMO it's really just that it's long and you have to actually want to just read it to Read it. It's not about later parts that turn people off, they don't actually get to those parts. People hearing about it later want to get to some part they heard about that seemed cool but then they get to page 1 and its long and a slow start. Slow in the sense that nothing crazy 'exciting' is happening, because the beginning is incredibly funny, and has a lot of interesting details and systems that they set up. Homestuck is not a casual read, and it's neither formatted nor structured like a traditional story. You have to go in wanting something truly different and be patient as it builds. It's like reading/playing Umineko.

It's always valid for people to have a hard line at certain bigotries to not read something, but they so often read as an excuse. Like you would be hard pressed to find any real stories (that aren't like. Bluey) that are completely "unproblematic." Frankly, at equal or worse levels. Everyone's throwing stones from glass houses. The truth is, they're just not interested in reading Homestuck (which is duh valid), and they feel like they have to justify it with "objective" reasons.

Also "repercussions for vriska being vriska"... She was beaten to death on screen. she gets more "repercussions" than the actual pedophile(s).