I dont underestimate that. I have seen very clear results (and i have been part of that content creating community). I was a mapper!
Maps barely matter to the playerbase since even after all this time, dustbowl, 2fort and goldrush are still the most popular maps by a huge diffirence. These are ancient maps and are similar to cs_office and de_dust2 within tf2.
New weapons also often backfired rather than were a good thing. The only thing people liked was that it created a hectic situation which completely altered the way people played. A fresh moment.
But at the same time, that hectic situation was a massive problem towards those that wanted a normal game. You had to dump in a hard class limit to get some degree of regular play, or just disable the weapons entirely.
The community at some point got massively split up, and each part simply degraded at their own pace. And the first part to die was the community server part. Because the average quality of those servers was horrible because instead of promoting good server groups, people rather abused it for advertising reasons.
Once those servers were killed, you only had a few places remaining for custom content.
Now yes, they were adding in community maps. But outside of borneo, those maps are generaly balanced poorly. Even the late valve maps were flooded with balance issues. Sure, it works for 6v6, but thats because 6v6 was a relatively balanced form in the first place (you cant lock down a game with 6 people).
This matchmaking system caused community servers, and therefor a lot of custom content to die. People stick to valve servers. Guess what that does to custom maps. It doesnt promote good balance.
Its that tf2 has a seperate competetive situation which uses their own mod and map pool, as thats still the main source of information regarding good maps. And as long as hots has such similar competetive pool, it can do quite a bit for the game since even without new maps, hero reworks can still shift around quite a bit.
That TF2 survived for over 10 years doesnt mean hots will, but even hots would still be able to survive for quite some time. It already is nearly half way, and would still be able to survive for 2 years with the content it gets now. Thats already half way. A quite decent result.
TF2 only became a goofing around nature type of game because it doesnt involve leveling in each match. But as it also doesnt involve a rank in pub games, it keeps that nature standing.
But what is completely forgotten is that many of the more skilled people at that time left PvP completely. Sure, they gathered a few new people in exchange for that. But the average skill in tf2 is currently that low that even with gold skills you would be GM.
TF2 dies in a diffirent way. And for many is already dead, thats why people switched to overwatch that easily when it was released. Even though overwatch gameplay wise is not even closely competing with it (overwatch has horrible balance and mechanics compared to tf2).
And that you left during matchmaking confirms what i am stating aswel. TF2 is dying just like this game, its just a diffirent pace. But remember that even after matchmaking was introduced, its taking a long time for tf2 to die. Hots might very well take a long time aswel.
. Could easily have been the same group.