Hi, I'm seeing a lot of complaints about teammates being bad, teammates holding you back, not being able to climb the ranks even though you're practicing and trying hard, getting a lot of losses after a lot of wins, etc. I myself used to have similar thoughts but have changed over the years, and I've since reflected on why I think these thoughts arise, which could perhaps serve as a kind of motivation or change in attitude.
Why your teammates seem to be the problem
One problem when you assess your own skill versus that of your teammates, is that your own knowledge about what to do is far from perfect, perhaps even in ways which you are unaware off. Dota is a very complex game and therefore it is possible that one player is good at something while another player doesn't even know that this thing is a skill one can have. Thus it is quite possible that you are looking at your teammates and noticing all kinds of mistakes which they don't even know they're making, while at the same time they're noticing mistakes from you that you don't even know that you're making. You're wondering why your team is full of idiots, and they're all thinking the same about you. Maybe you're a better judge of which fights to take or not, and maybe they're better at judging the correct objective to go do. You wonder why these idiots don't want to take a fight, and they're wondering why you're so obsessed with pushing the wrong lane, for example.
On top of that there's a bias in human thinking where we judge ourselves by our intentions, but other by the consequences of their actions. You went in for a kill and died, and you think "well it was worth the try, I'm only a support and it was close"; Then you see the other support going for a kill and dying and think "look at this idiot, he's dead again".
Your impression of what it takes to climb the ranks may be incorrect
You're not the only one trying to get better at this game. You're not the only one playing this game all day long. If you're improving, but just as fast as everyone else in your bracket, you'll deservedly stay there. You may feel like playing a few games a day and watching educational videos now and then should cut it, but there's no reason why it should, as many people are probably doing so.
Also, it's not enough to just play decently well. When I speak to friends or see certain posts about this there often seems to be this feeling that just because they had some good games, this demonstrates that they should have much higher MMR. Or just because they're "doing their job", getting an average amount of kills, deaths and assists, that they should somehow be climbing. Or because now and then they go 20/0/10 their losses are obviously to be blamed on others or the matchmaking algorithm. This is incorrect. If you want to climb the ranks fast, say at a 60% winrate, you need a hugely disproportionate amount of positive impact in your games, and you need to get that somewhat consistently. (Or you'll lose the MMR again) If you have a good game when your allies do well but hardly ever carry an otherwise bad game, then you probably just deserve to be where you are.
You affect your teammates
The last point I would like to make is perhaps the most significant. Often when you have bad teammates they can be a reflection of your own playstyle. Maybe if you'd pressure another lane harder, your carry would have more space to farm. Maybe if you ganked his lane earlier and more often, he would have a better k/d. I recently tried to coach a friend of mine who was consistently complaining about his team being passive and mediocre; all while playing incredibly passively, blindly following the same build every game. If you're not as much of a help to your team as the enemy counterpart is to his team, expect your team to be more mediocre. Of course now and then you run into blatant griefers who maybe had a bad day or something, but often enough your bad teammates are just a mirror of your own playstyle.
What climbing is like
I was stuck at my MMR for a while and didn't play a lot, until at the start of 2020 I really started to pick up the pace and I climbed 2k MMR that year. Now I'm basically just hovering around my new MMR. I can tell you that the experience of playing around your MMR is exactly as some people describe their 'problematic' situation: You win or lose 50-50, after wins you get losses, and the game seems to depend on your teammates, who seem to be 50-50 between being good or bad. I can also tell you what it was like when I was in the middle of my climb: I felt way more in control. When you're actually better than your rank, in my experience you don't feel like games are as random as they used to be; you don't feel like you "finally got decent teammates"; you feel like it doesn't matter what teammates you get, you'll have an extraordinary amount of impact and win significantly more often than you lose because of that. I would often win games even when they started with the enemy carry popping off; I would consistently be ahead of others. This is not the case with the people I'm playing with now. Whether I have a good or a bad game is kind-of 50-50 depending on my teammates, which is exactly what you'd expect if you are at the rank you deserve.
Forced 50% and other matchmaking shenanigans
One thing to keep in mind when you think the matchmaker is working against you: If matchmaking is working properly, you should have a 50% winrate. Only when you are consistently underperforming or overperforming relative to your rank can you expect to have a significantly lower or higher winrate, but the MMR system is supposed to get you to your true MMR and so eventually you'll start to go 50-50 again. It is part of a well-functioning matchmaking algorithm that any undeserved gain in MMR is promptly lost. I suck at judging my own skill level and you probably do too; one shouldn't pretend that one deserved all the MMR one's losing when one couldn't possibly know that.
An alternative attitude
The one central message I would like to be this: Your MMR really reflects your skill; perhaps not to the accuracy of ~50 MMR, but roughly, it does. You don't deserve every win or every loss, but there's such a great extent to which you could affect games, it's insane (just look at what the occasional smurf can do). Don't just assume you're better than your rank suggests; you probably don't even know what that looks like. You can climb even when you don't get lucky with teammates: The people around you probably aren't that much worse than you; and you can gain MMR without having the system make you lose it again. Only if you start consistently playing better, of course; but improving does really pay off. As Dota Youtuber Henry once said when asked (I paraphrase) "How do I win with these idiot teammates": "Just be better."