As long as it fits you, I say go for it. It is likely a bit old school XC geometry but you can learn the skills and what kind of riding you want to do. You will be able to get the necessary level of fitness. When you out grow the bike for your skills then it can be your commuter or bar bike. But it is your money, not mine.
As yapidoscar said, as long as it fits i’m sure its fine. Heres a little story for ya about the bike someone rides. Few weeks back i purchased a gravel bike to change up the work out and improve my endurance. First real ride clipped in i headed out from my house and within 5 minutes came up on another rider. I pedaled up to this guy and he was probably mid to late 50s in age and on a old mongoose mtb clipped in and what looked like from behind as a tried to catch up was a slightly twisted frame. As i made the effort to get by him said good morning and headed to the gravel trail. About 6 miles in i took a few minutes to make a adjustment and here he comes. He was no joke and was gone before i could get back to pedaling . My point is it doesnt matter what you ride. Until you get some fitness nothing will make a difference and that will take some time. You have to put in the effort and discipline and enjoy riding is what matters. Dont spend alot but get a bike that fits and tailors to your needs and enjoy the rewards. Also ,diamond back has been making excellent bikes for a long time.