If nobody offers a default filtered experience then most people will refuse to join.
If you want to offer a default filtered experience, you do that at the instance level, not as a frontend dev.
And you absolutely do not do that in secret, deliberately not informing users of the 'filtered experience' they're signing up for and disguising the filtering as technical failures.
If you want to start a Lemmy instance for centrist normies that blocks its users from all the 'extreme' stuff (and you are transparent to those users about what you're blocking and why), that's perfectly fine. Go ahead. I don't think your "I'll decide what should be censored for you" approach will be as popular as you think, but there's no reason not to try it.
Maybe you should try your own advice.
I already do. Regularly. Which is why I recommend it. What, are you suggesting I should block you or something? Honey, you're not nearly annoying enough to block. Not yet, anyway.