I guess I have come to feel or go through that same situation, when adult life comes everything changes. At least me, I always try to keep one or another game that keeps that spark alive, although honestly sometimes I get bored, but still there is always that game of yesteryear that makes you come back, I don't know about others, but it happens to me.
Regarding the game, Playing Ultrakill reminds me of that first installment of Doom. These games, even though they lack a clear narrative, have that plus to end up hooking anyone. My forte is not the shooter but that doesn't stop me from knowing that these games are still in the trunk of memories of many.
I think it's a Doom mashup and that's why I found it so fun to play, I hope you can try it one day!