This is true of all Windows versions, but was particularly true of Vista, and of course the reality was:
* Very few people carry out a clean install when they get a new computer. This is as true today as it was ten years ago
* Hardware manufacturers loaded the PC's up with terribly written adware before shipping (this situation has improved slightly)
The requirements for Windows 10 aren't that much more than Vista, so, the average person would get their new Vista PC running on a Core 2 Duo/Pentium D and 1-4GB of DDR2 Ram, loaded up with crapware and not do a clean install, and it would run horribly.
By the time Windows 7 came out, the PC manufacturers where writing slightly more efficient crapware, hardware was generally a bit more powerful, and they had fixed a tonne of bugs in the OS itself.