He was really old and lived an excellent death doing what he loved... I can understand fans celebrating his life, but the mass funeral, largely conducted in news articles and social media pieces, is a bit overwrought. Don't feel like you're weird for not engaging with it.
The real sign of apathy is not caring if people who are real to you personally die, and I think a lot of suicidally depressed people do detach from life a bit as they question its value and wish to renounce their own, at least for a while.
To be honest I didn't even know who Stan Lee was, I just went about my day. I didn't want to upset anyone who loved his works, but I wasn't going to throw myself on a pyre over a stranger either.
The only celebrity death I've been affected deeply by in recent memory was Prince's, due to the circumstances and the inspiration his music gave me. This might sound cold, but I find the hysterical media-driven mourning for every single famous person that dies, including ones who have lived to ripe old ages in fine health, a bit detached from reality. I think it's within a normative range to feel saddened at those who want to live losing their life or mourn and commemorate people you admire, but the celebrity death craze has become a real marketing event (remember that one year?) and is part of a culture where we fetishise avatars of the ruling class.
I have mourned other strangers who impacted my life or who did a lot for the people. And I understand the average fan feeling some loss. But a lot of the craze you see isn't that, it's branding by the same parties who help sell an inner world built around media consumption. It's safe and fluffy tragedy porn that redirects and warps your emotions and has become more sensationalised over time. Don't let it shift the window on what's sane to you just because you once would have wholeheartedly indulged. It's sad when the happily living pass, but we don't die without our cultural heroes.