I know that feeling. I really despise the match making at the moment.
I to would like harsher punishment for repeat offenders maybe give one game a week where you only lose the normal amount in ranked but every leave after that increases the loss of by say 200 points and the bans also increase.
I had a QM game the other day where my ISP partial dropped out and was getting basically 2s lag spikes. Everyone in the team said it would be better with an AI. So should I leave and get leavers status or stay and be worse than an AI? I didn’t play another game until I got my internet sorted but sometimes it happens.
Also I think in rank if you have a leaver in your team you should lose less rank points etc.
How to get better at the game?
Be very self critical - try to find out where you need improvement. That’s the name of the game for almost every eSport Game --> constant self improvement.
Everyone is ignorant to some extend so you might not find out where you need to improve. Watch replays and focus on your impact on the match.
Get inspiration and deeper insight from high level players: (Youtube/Twitch)
Practice.
Mental and physical state (being stressed/tired/drunk vs well rested and a focused mind makes quite a difference)…
Rankings and MMR all happens passively and you should not really worry about this. Just focus on your own improvement and the rest will come hand in hand…
Even when you lose because of AFK’s - the lost ladder points don’t matter. The only thing that matters is if you were able to use that match for some self improvement.
I actually do that a fair bit of watching… probably to much 
Usually if im feeling tired/stressed/drunk i will be watch vods about HOTS or something else but sometimes the stress is calles by HOTS HAHAHAHA.
I know I improved on map awareness so much after i first started HGC.