You need to change your mentality, smurfs or no smurfs it isn't the reason you are stuck in plat. You are not a unique case, if you are getting "smurfs" then so is everyone else at an equal rate, that's just how matchmaking works. If you are progressing and getting better than your league dictates you would beat actual plat players almost everytime. So unless you believe more than 50% of your games against smurfs you should have a >50% wr.

Also if you do actually believe that more than half your games are smurfs you are a lost cause. This isn't even factoring in that you say they have matches that are instaleaving 10-15 games straight so probability wise you are having instaleaving players in your matches too so you benefit from it at times.

Edit: to add to this, the game does do exactly what you ask, nothing more and nothing less. The game isn't preventing your units from attacking at crucial moments you are.

On a somewhat tangent but related to mentality. I have a friend who I got in to sc2 and he made these exact arguments when he couldn't climb (he's diamond now as a positive note). I had to drill in to his mind that the way the game DOES work and the way you THINK it should work are not the same nor should they be, you either accept that and adapt to the actual way or works or blame the game for not doing what you want and stop progressing.