The prequels are entertainingly bad, but if that's all the PT gave us, it wouldn't be very interesting. Why the PT worked and the ST didn't is, quite simply, George was right about what worked with Star Wars. No, not the actual movie making process, but the product. The PT made a bunch of money, but Lucasfilm went absolute ham for the period the PT was being released. One movie every three years, almost like clockwork, and an absolute deluge of PT related media expanding on the ideas in the movies. And some times other, unrelated to the PT media just riding the renewed wave. A lot of it was mediocre, but little of it was as godawful as the PT movies themselves, and among it was some of the most beloved bits of Star Wars outside of the OT by a wide range of fans. The PT era was an impressively fertile ground for Star Wars stories, even if they had nothing to do with the actual in universe PT era.
The ST totally botched this. They too, made a bunch of money, but thought that the Star Wars movies actually being good movies mattered. They fucked that up too anyway. Nothing in the ST was as much as an abortion of filmmaking as the PT, except maybe bits of TRoS. But there was no real similar boom in Star Wars media, for better or ill. The era was marred by giving EA an exclusive license and then them shitting mediocre, boring games until maybe the last minute with Fallen Order and perhaps the upcoming space combat focused one. The side media was stuck either doing shit in the OT or PT, with almost nothing worthy of note tying into the ST. The ST was just too boring to produce anything of value, since there's no space to do anything interesting during the movies' time period, you have to wait until it's over to do anything after, and anything before it will be fucked by TFA almost literally blowing up and/or killing everything you could've thought of. Incidentally, this is sort of the OT problem, except way worse than that period ever had to deal with.