when regulus died he didn’t renounce the pureblood cause, he just defected from voldemort because voldemort wanted to be immortal, etc., so pretty much died being a racist that still wanted to blow up muggles, he wouldn’t come back from the dead and suddenly join the order or even be polite to harry + co
jesus christ regulus didn't even really care about or believe voldemort's opinions and his cause, does it matter he was a death eater and you think he was a voldemort fanboy? he was a death eater because of his family probably, or maybe later he realized he doesn't agree with lv's opinions. and how is it against his character to ship jegulus when we know little about regulus' character?
We know enough about his ideals, which matched perfectly with his family's as told by Sirius himself. Your stupid little cutesy headcanons don't change that. His family was actually opposed to directly joining Voldemort instead of just supporting him from behind. Why would he cover his bedroom walls with Voldemort's newspaper clippings if he wasn't a Voldemort fanboy? Why was he the favourite coddled child if he didn't agree with his family's views? Your fanfics are not canon lol it makes me laugh that you say he didn't agree with the Pureblood cause when the little information we have about him suggests that he did.