I could point you at the wikipedia article for the shortcomings of Dobsonians. They are, however, unrivaled for visual astronomy and ease of use. The problem for beginners was that before the dob, the market was dominated by junk scopes at the low end and astrophotography scopes at the other. When my wife says, "What's that bright star?", it takes ten minutes to set up my dob, and show her Jupiter. Grandkids, wives, sweetheart, and friends don't have the patience of equatorial alignment.
For my own use I have a really superb refractor with great lenses