Binge-watched this a few years back on YouTube as I was too young at the time it aired.
Agree with OP that Sparks was a horrible actor., far, far worse than anyone else in what quickly became a soap opera. Wasn't really his fault as he was a standup comic who would probably have been fine on a Fully House style sitcom, but every time he came on it seemed like a character from a different series wandered onto the set and he came off as special needs and you wondered why any of them were friends with him other than pity or fear of the overbearing mother.
I thought the rest of the cast was fine, Harold actually had his moments, all the "acting with his looks" stuff and Gless was way too over the top too and annoying AF.
It was interesting for me to see that they portrayed a range of levels of masculinity/heteronormativity, as most TV shows (Modern Family, Will and Grace) still portray gay men as minstrelly mincers (or the joke is "Ha! He's gay! But you'd never know it! (Brooklyn 99). So props to QAF for managing to get that right.
After bingeing, I looked into it a bit and found out that:
* Battle between Sparks and Harold/Harrison was because (a) Sparks was supposed to be the star but Harold had an army of mad fraus who were in love with him and made him the focus of their attention.
* Harold/Harrison also pushed back on producers to stop making the show suck so much with corny soap opera plots and then decided to end the show after 5 seasons, but Sparks just wanted to keep the gravy train going and was pissed. (Harold/Harrison were actors and thought the show would be as good as UK series and thus good for their careers. Sparks was a stand-up, he just wanted paychecks and residuals.)
* There is still a small army of fraus who are obsessed with the show and with Harold and Harrison. Some of these fraus believe that Harold (hetero) and Harrison (homo) were a couple during the show and after and have all sorts of Pizzagate-level theories on that, many of which were once shared on a gay message board called Datalounge ;)
* Harold (was was hot AF 20 years ago when he was in the show, IMO) had a post-QAF career and a good role on Desperate Housewives, but was in a bad motorcycle accident which seems to have derailed his career. (Most of you probably knew that already.)
I'm surprised Showtime doesn't try and do a reboot given all the other crap from that era that's being rebooted.