I use a lot of assets I made or have bought/downloaded, and there is nothing wrong with using premade assets as long as you follow agreed licenses and dont render the asset alone and talking about how you made it, also assets themselves won't look always like you want them to so change them up a bit to make them fit your need's.

Best assets most of the time will be self-made or bought from big asset libraries like Quixel.com or Textures.com [ Not Sponsored Btw ]

Hope this helps you guy's out, if not you can always ask me questions. <3