I think people have slowed it down for sure themselves with the playstile and with the "meta", but from a game developer point of perspective, if something has a tendency to act a certain way, it is very likely caused by the system of rules which it is bound by and by changing the rules and parameters, even slightly, you could potentially redirect the course immensely.
I have no clue what to change in the system however to fix it and from a developers point of view, I would start with incremental test changes to see what effect they have and with actual real time data, adjust accordingly.
However the problem here is that the tf2 community, thanks to its own environment, is super conservative and would rather theory craft theoreticals and come to conclusions they 'think' to be true, rather than to actually make changes and see how it would affect the gameplay. Most of the time, if a change is made by the community and it has negative effects, the change is then reverted and the idea neglected and everyone goes back to their old comfort zone they were so use to, even tho the more healthier thing to do, if u actually want to make a change, is to adjust the parameters of the adjustment. The tf2 community claims to want to grow and fix problems, but essentially we don't, because growth to us is only acceptable if everything stays the same - contradictory? Yes!