You can certainly buy pre-built, even customize one to your liking but know you'll pay a premium for a decent one. They pay less for parts than we as individuals do and you still have to research components thoroughly because they won't. They'll put it together and ship it to you without a care for how it all works together. Know that they have at least one employee that has to get paid, working in a space that also has to be paid/rented for, now you figure out who eventually pays for that. If you arrived at the conclusion that it's you, good guess.
There are so many guides and youtube videos out there, the excuses for prebuilts from 10 years ago are all but gone now.
If you still insist on buying a built PC, you are better off hunting down PC's that are getting parted out on PC specific for sale/trade forums. If you don't find what you look for there, I would at this point seriously consider building one, you can find great bargains on parts. Most trading on tech forums is done by people who accepted tech depreciation as fact of life a long time ago and don't stubbornly stick to unrealistic pricing. I would rather pick up a used or older power supply from a hard forums user than whatever junk prebuilt sellers try to increase their margins on. When these guys buy new, better believe they did research and the value of doing the research is passed onto you when you trade with them. You can also buy windows for a lot less than retail (legit) on PC specific forums.
You can mix and match used and new parts to get more bang for the buck. It will take some research but you'll be better off in the long run. Good luck.