It's one of the most important game franchises of all time and I'm really glad that I experienced the original when it was new (well, I was a bit late to it, but time moved slower then), and at a time when it had a formative effect on my life.
I was playing Doom 1/2 when I was 10-12 years old, at friends houses who had the right computer OS+specs to run it. I wouldn't say it was solely responsible for setting me on the path towards other adjacent media like horror movies, metal/punk music, etc but it was definitely an important stepping stone along the way.
That said, I didn't spend too much time with it compared to other games. I was never very good at it, preferring instead to watch my friends play since they'd had more practice time. Over time we gravitated towards newer games, and my time with Doom was over for a while. (I was disappointed by Doom 3's gameplay, possibly exacerbated once again by my computer being underpowered for the technical requirements to enjoy it)
Fast forward to 2020 and we're all in pandemic lockdown. So I fired up my ps4 and went looking for some "comfort games" to play - old stuff that I knew I'd enjoy and wouldn't break the bank. Sure enough, I found a cheap Doom bundle: Doom 1, 2, 2016, and Eternal. We're back, baby!
I ended up beating the original gen and their available Unity port WADs (e.g. BTSX) on Ultra Violence, beat 2016 and Eternal on Nightmare (no ultra nightmare for me, though I did put in some honest attempts). And Ultra Violence for the Eternal DLCs also. I still will pop on Eternal for some casual slaughter - I really love the dynamic combat.
Along the way I got interested in some Doomtubers as well- Zero Master to see, well, the master; but most importantly Decino who I still am playing catch-up with trying to get through all his content. My wife sees me watching his vids sometimes and "can't believe you're still watching Doom".
So yea I'm a fan.