You darn kids with no appreciation for the classics, get off my lawn! ;)
Scooby was my main Sat AM staple in the early 70's. The animation isn't better or worse than any other show that was on the air at the time, except for Filmation. It's harder to see what made it unique over 40 years later, after umpteen spin offs, clones, reboots, and a now a direct to video movie every three months. (Or so it seems.)
The concept of a "scary" cartoon was mildly controversial, especially in a climate where self appointed do gooders were doing everything possible to make cartoons as bland and inoffensive as baby food. Scooby Doo's scares were safe. The gang was never going to stumble across dope smugglers, or hippie death cults, or real ghosts.
The two biggest mistakes of later incarnations were Scrappy Doo, (just about every other cartoon got an annoying pint sized character in his wake) and making the ghosts real. Vincent Price made 13 Ghosts of Scooby Doo better than it had any right to be though.
A friend of mine is a life long Scooby fan, and he grew up to be a paranormal investigator in his spare time.