GT3 and GT4 were released when people had online access. Those threads didn't have the toxicity of threads since GT5. I'd say it's more to do with the general nature of the specific game that drives the issue.
Yes there is certainly that as an element but its human nature anyway to always focus on the "bad" not the "good" - just look at the news. Its only news when its controversial etc - very few heartwarming newstories except for the obligatory ones at Christmas.......
Its interesting you mention GT5 (and GT6 to a lesser extent) as this site was certainly pretty toxic thread wise during those times - been a long time lurker since 2010 so was around then but not posting for various reasons that no longer apply now. In fact I highlighted GT Planet as a potential resource to fellow colleagues who were enjoying the GT PS3 games and they thought the site was very, very negative.........
Frankly I don't see that level of toxicity now for GTS. It was inevitable as a "reboot"of the series it would cause polarized opinion but I see quite a few posts saying in effect that its better than they expected, even without GT League. I also see posts asking for help in improving online racing performance so the sportsmanship message resonates somewhat too. Note too that many believe they received value for money from this game and a number of posts make the point I'm unhappy with X but overall its a good game or words along those lines.
Fully aware it could become more toxic should PD not live up to their commitments by March 2018 including GT League and 50 DLC as the PS3 era was such a searing experience for some that there is a lot less faith in PD than pre GT5 and it would not take much to see the enmity resurface.
Interesting PD seem to have taken that on board focusing on quality before quantity and a published plan (except tracks) for next few months and critically GTS is not a buggy mess at launch so it can be built on in the future.
Inevitably though when the intent is to appeal to millions of players from all walks of life it will not match perfectly the desires of an individual - just like when you buy a car from most manufacturers it is made for many not an individual unless you are a multi millionare of course !
p.s Fully agree unlike some comments in this thread that individual is of course welcome to share his thoughts and wishes i a thread/post (within the AUP of course).