So I've been into Beyblade since I was 10 (I'm 19 now) and I took a break towards metal fights end, came back during Cho-Z of burst. I was wondering if trying to build up a metal fight collection from scratch would be worth it in 2021?

I think it would definitely be worth it, the trouble is finding legitimate metal fight Beyblades as they seem almost nonexistent these days. There are a few legends series beys (meteo L-drago, burn fireblaze, rock Leone, galaxy Pegasus) which are almost certainly legit which I think is a good place to start your new collection 👍