750$ PC-s can be powerful if you know what to put in there. In my opinion its a short answer - it depends on the usage. Of course you wont get a 750$ PC to mine insane amounts of bitcoin for you, but if you want to play games and upload them on youtube, then yes.
A must get on a 750$ PC is a GTX 1050ti or a GTX 1060. If you want to go cheapwith a GTX 1060 then an 8th generation Intel Core i3 is a great choice. If you have some extra money left then try to get an Intel Core i5-7400. For example a 1050ti and 8th generation i3 in my country go for 422USD.
Note: Always try to avoid Pentium proceccors, in my opinion they are useless.
I hope I helped you with my first and short post :)