I would not say its bad quality, but its definnately not a premium quad copter since it is not very expensive, this is why it is good for beginners as most people might crash their first quadcopter. We sell it as it is one of the cheapest parts you can get that still work! But I dont think you will do very well if you take it to a FPV racing event… To make it better I suggest you just replace with brand name motors/ESC. The flight controller and frame are still plenty good enough.
For example I would suggest you upgrade to 20A Chaos ESC, and 4x CF2205 motors and you will have great flight performance. In general if you are looking for your first quadcopter to build then I can suggest our more recent martian kit - https://www.unmannedtechshop.co.uk/martian-iii-diy-fpv-racing-quadcopter-beginners-kit/
If you want to use the best gear, it will fly increddibly fast, but then you are looking at over £100 just for the motors, and we are selling the entire quadcopter for under £85