The funny thing is that 720p was not really a thing when WoW was released, and a comparable resolution (1024x768) would have been considered fairly nice back then. I reckon a lot of players played WoW at a resolution worse than 1024x768.
Yes, it was. The first HD game was shown in 1993. HD sets were released to the consumer in 1998. My PC monitor was 1280x1024 in 2003. PS2 and Xbox could output 720P and Xbox up to 1080i. Laptop screens of that time period were typically 1280X800 on a 15" Laptop.