I do think dota2 has a lot of issues but not the lack of surrendering.
The mute system needs to be revised heavily, at the very least you shouldn't be able to report for communication abuse if the person is muted, just add throttling to automated messages if there's not one already, tweak the throttle on pings a bit(need to be able to ping slightly more since apparently it is very restrictive) and that's good.
Second, add a tribunal thing, have all the communication reports go through that shit instead of being automated. It's still not gonna be 100% fair due to people farming tribunal, but it's gonna be better. This will require a large amount of work though, and considering how little ressources they seem to have on dota2 at the moment, I don't really know if it's feasible before next year.
Finally, remove the cap on reports for griefing and such. However add a warning that all these reports will be reviewed(and do review them) and if a report happens to be unwaranted, then the person who reported will be flagged for bad report. 3 flags, temp ban+low prio for a long time, basically a deterrent for report spam shit so it's more manageable to sift through the reports. Maybe keep the cap but increase it, maybe tie it to games played(1report per week, add 1report every 10games played). Potentially also add weighting to reports, people who report rarely but play a lot would get a bigger priority when reviewing reports, as they'll less likely to be people reporting for small shit, which should make it easier to punish the people who need punishing the most.
Edit: I wouldn't mind a 40+mins surrender, most people asking for surrender want a 15-20mins one like lol or hon had(I believe they moved it to 30mins in hon). There is a built-in surrender feature as I said though, if everyone has given up and want to end the game, you just have everyone leave. 30secs later the game ends, no abandon(unless you only have less than 30secs left to reconnect from a previous disconnect)