I just don't get why one would write walls of text about the game he doesn't like.
Because it promised to be a spiritual successor to one of - if not the - greatest RPGs of all time, and then utterly failed to live up to those promises. If this was just simply a bad game then people would write it off and nothing more would be said about it. But because of promises being made and expectations being raised, people are going to be pissed off when it doesn't deliver.
If it makes you feel better, inXile did do a good job on Wasteland 2, and may do a good job with Bard's Tale IV and Wasteland 3, but for whatever reason they messed up badly with T:ToN and people aren't just bashing it because they're trolling. Sometimes I see people hate on legitimately great games on here, like Pillars of Eternity because they think its cool to be edgy and hate for no good reason. But in this particular case with T:ToN that hate is warranted, and its not just people trolling for lulz.