I don't know about TNG but Star Trek TOS very famously had the opposite situation of Game of Thrones lol
My point is that GoT already exponentially increased its viewership year over year, hitting a peak with S8 and the finale that, even if people absolutely loved the ending, how much more room is there for a now-defunct series to grow? I bring up Breaking Bad because it's the same thing: a show that started relatively small (much smaller than GoT's first year), was discovered on streaming, WOM caused a surge in viewership in its later seasons, then peaked with huge numbers in the final year. But that popularity didn't translate into an equally or greater life-after-death run for the show on streaming, nor did it carry over into Better Call Saul. I don't know what genre has to do with it either - arguably something like fantasy is a harder barrier to entry for a mass audience than a more straightforward western/crime drama like BB.
As for whether people want to revisit Westeros post-S8, well, it's kind of hard to see if it'll track like other fantasy IP since there's been no new GoT product yet right? House of the Dragon will be the first real test of how viable the franchise is after GoT's finale, though I also don't expect that, no matter how good or bad the show itself is, it'll just ever see numbers similar to GoT as is usually the case with the spin-offs. For now, it's probably a little bit instructive to look at the HBO tweet in the OP, which has 16x as many likes as many comments. Even if you think every single comment is super negative, that's way more positive sentiment than negative. I don't want to read too much into the engagement on a single tweet, I just think the degree to which many think this brand is totally dead now is very overstated.