Is it really boosters and smurfs ruining the game?

Hello there. I've been playing dota 2 for 8 years with a few year long brakes. I've mostly been playing on eu/Russian servers. I had around 3k mmr when i first calibrated, and right now I have 4700 mmr and rising. I main 3rd and 4th positions. I had recently got an opportunity to compare different ratings. I played on 2 of my friends' accounts, first one with 300 mmr and the second with 3400 mmr.

Here's what i've learned from that experience:
1. Smurfs and boosters on both occasions are not that often encountered, and, to be fair, not that much of a deal. They have a 50/50 chance of both being in your and your enemy's team. You can easily counter them through proper teamplay and map movement, blocking their jungle and communicating with each other.
2. The main issue people are stuck on their rating is rather a lack of proper communication, immense toxicity and inability to learn. On a low rating you can use a strat you could be using on a 4.7k, get flamed, but convince people you know what you're doing. But on a 3.4k mmr you will get flamed, but no matter what you actually do, no matter how hard you work on the win, people will not lose their toxic attittude, start insulting their other teammates for literally any mistake and mute everyone thus making most of any macro movement on the map impossible. These people will pick the worst possible hero there could be for their position (3 pos weaver, hoodwink 5 pos leshrak). They will start throwing a game as soon as they find an issue to complain about.
3. Leading from the 2 previous points the result is having 3 16 score at the 15th minute every 2nd game. After rewatching it the problem is not that the enemy team plays better, or that there are boosters against us. The skill level is somewhat equal. It's the communication inside the team and if the enemy team is more mentally stable, they have a higher chance of winning.

Please share your thoughts on this.