Should be ok, tyre choice might be an issue. It's not a KTM or a BETA & it's light years ahead of the XT, must have been a great bike when they first came out, the fact that GB raced one is proof I guess.
We have a guy in our group with a KTM 300 EFI 2T & he can't keep up with either my TTR or WRR so apart from tyres weight is the other problem. Would you believe my TTR is lighter, has more travel & better ground clearance than my WRR.
Newer bikes are generally lighter, faster with better suspension. But they are also expensive to buy and more maintenance intensive/$$$$. Newer race bikes require engine rebuilds at 40 - 60 - 80 - 100 hours etc where there's 20+ y.o. TTR250's still getting around unopened. Yamaha did a great job in the early 90's designing this bike it handles great.
It can get left behind by higher HP bikes at higher speeds. But not necessarily in tight bush where HP isn't so important.
Basically if you are racing to win or for sponsorship, race the best bikes. Racing for fun the TTR will do ok and can embarrass riders on new bikes. The old saying 90% rider 10% bike holds true IMO. Race the TTR and have fun. And put up pics!!
The TTR can be improved easily, depends on your priorities and budget. Strip off the unnecessary weight, derestrict and rejet and enjoy. I would get suspension professionally set up and a performance muffler but that's just me.
Off topic, but, kaos, looking at your profile picture, i see your bike has USD forks, did you do an entire front end replacement or did you bolt it on to the stock triple clamp?