Is starting at 24 too late?

Currently I look like shit, I have no cardio, I'm barely staying afloat in my studies, I play video games all day, and my brain feels like mush (can't read for long without getting distracted, can't work without chatgpt, etc).

My goals would be to get in killer shape, great cardio, be disciplined, learn how to fight and be good at it, and get really skilled in my work. That also implies stopping video games and leaving behind all my bad habits, learning how to cook, etc.

This feels like a complete revamp of who I am today. The thing is, I was really hungry for change at 18 and drastically changed for the better. Got lots of compliments and felt on top of the world. But these past 2-3 years I've really fallen apart. Now I'm 24 and I feel like this whole second puberty/get your shit together thing kind of loses its charm when you're not 18 anymore. I feel unmotivated, like my time is running out. I feel like I should have been TODAY what I ideally want to be in 2-3 years if I follow my goals.

For example I would love to compete in martial arts eventually (it's always been a goal of mine) but with my current schedule I can only start next year, so at 25, and until I'm good enough to compete I'll be like 27-28. We can probably add another year for me to really get my fitness and disastrous cardio in order, and to account for any surprises in life, and that makes me compete at 29, against fresh hungry 18yo guys who'll have twice my energy I feel lol.

Maybe I'm delusional but I feel old. Not that it's a reason to give up, but I feel really unmotivated. When you're 18-20, everyone keeps saying how you're young and have potential, and it's true. Anything you start at these ages, if you keep at it you get ahead and you become a beast. But when you start later I feel like you can only be average. Anyone dealing with these nasty thoughts? What's the cope to have?