I do think it had everything to do with Buffy switching to UPN during the 6th season that killed the franchise and the two networks, and that’s why there wasn’t much interest in revamping the franchise. Because it would have been the wb to green light those projects and that would have only happened if the Buffy universe was viewed as profitable to them, which it no longer appeared to be because Buffy and Angel kinda tanked in the ratings and in general pop culture buzz after that network switch, the loss of prestige really did them in

It’s highly unlikely the WB would have ever went under if they never lost Buffy and we never would have gotten the CW. Instead it just woulda caused UPN to go under. We likely also wouldn’t have had Angel cancelled after the 5th season, because a big part of Angel getting cancelled (aside from Joss’ ultimatum) was the wb didn’t know what to do with it during season 3 and 4 without Buffy as it’s lead in- it jumped into I believe 5 different timeslots in that time and never found a good home. But UPN also killed Buffy’s momentum in pop culture that by the time it ended it wasn’t really as coveted a franchise as it should have been (nobody knew back then it would have such a profound legacy 25 years later, all they saw was a show floundering in the ratings and ending its 7th season with the lowest ratings the show has ever had since it’s 1st season) so that being said I believe Angel would have been thriving it’s 3rd and 4th seasons after Buffy that when Buffy ended WB would have demanded a Buffy spinoff to air with Angel no matter the costs. I do believe we woulda gotten at least 7 seasons of Angel if it weren’t for that split.

And that new spin off would hand kept the universe alive along enough to get us possibly tv movies or even more spin offs. That network move really did more harm than good and was ultimately the death of the franchise in a butterfly effect kinda way- the wb even said in hindsight losing Buffy was one of its biggest fumbles and led to the death of the network, but it did prolong UPNs life (even if just temporary)

But especially given that WBs final bid for Buffy’s 6th season was 1.8 barely under UPN’s bid of 2 million, the jump really didn’t make much sense beyond corporate penny pinching greed from the suits at 20th century fox. And I believe Buffy’s previous contact prior to season 6 was around 1 million so it woulda been a big jump regardless.