Play games you normally wouldn't. I was in a similar position until my friend insisted that I try few of his recs. I played mostly western RPGs, metroidvanias, FPSes, TPSes, stealth, and strategy. He insisted I try Ace Combat 7 when it was on a big sale. I did and a whole new genre opened up for me. Playing the game felt fresh, I was learning new stuff, discovering mechanics, and it was the closest in decade or two that I felt to like a kid and getting into video games again, where everything is fresh and interesting. Same happened when I tried adventure games, got back to playing racing games first time since I was teenager, and fighting games are next on my list to try.
Beyond that, if videogames are your only or main hobby, try doing something else like
>>1066640 suggested. Preferably not in front of the screen if games take up a lot of your time already. If you enjoy expression, try dabbling in a creative hobby. I found that it's best to have a good mixture of hobbies that:
>keep your body moving, like hiking, running, lifting, swimming, tennis, etc.
>focus on self expression or building something - arts, journaling, woodworking, home improvements, modelmaking, legos, gardening, caligraphy, cooking fall here
>keep you learning and mentally active - languages, reading, coding, travel, etc.
>consumption hobby that will give you things to talk about and draw upon for other hobbies. Travel, visting museums, consuming media all fall here.
Many hobbies cover two, three, or all categories. Or go well with each other. Any new hobby you pick up will involve a lot of learning and that will engage your brain by default. It's good to rotate hobbies a bit too, especially the physical ones. If all you do is run, it will eventually get too easy and might result in an injury due to overwork. Mixing it up with swimming, lifting, and another sport, and rotating them keeps things fresh.
And coming back to games, completion ism does suck fun out of it like
>>1066630 pointed out. It's definitely there to keep people playing games longer than they would otherwise, and locked in on platforms they use. I used to care too much about getting to 100% and it did suck fun out of the games. Once I got older and realized how precious time was, I stopped caring. I only 100% a game because I liked it so much I finish it more than once. First playthroughs are usually best done blind without worrying about even finishing the game anyway.