I get what you are saying I just don't think it has to get in the way of having a fun gaming experience. I have played with rushers, I just let them get on with it, sometimes I can keep up with the faster pace, sometimes not, either way there is still plenty of fun to be had working to the obj and I end up arriving half way into the capture. Sometimes the extra kills you get puts your points ahead of the rushers which does kinda make me chuckle. Yes it is better when there are no rushers on the team and in plenty of games there aren't. Some games are faster paced than others. If there are loads of rushers and the pace is just too fast then I just leave and find another game but I find that the exception rather than the rule.
As you say insurgency is never going to be squad, insurgency coop is the most casual of casual game modes where you just jump in, have fun, hopefully get some teamwork (not usually much mind) and get a nice score along the way. Especially if you're not in the mood for a more sweaty pvp game.
If the points were tweaked so that rushing to get points did not make big prizes then you would get much less rushing. I think it would get pretty dry for a lot of people if there was no points except team points which nobody is going to care about anyway because of the casual nature. People enjoy competition and I don't think that is going to change any time soon, even as you say it is only competition against other team mates. But even in pvp people care about whether they are winning as a team and getting good kill streaks to get closer to the top of the team score while still factoring in teamwork enjoyment, what is happening on the opposing team's score board is much less important, so therefore by extension playing against bots does not really change that dynamic a great deal. After all it is by definition a 'game'.