Don't worry OP, absolute decentralization is impossible, there are ways to perform take over on every decentralized system. But your reasoning aren't related with decentralized system weakness.
1. The lack of authority from the crypto founder to resolve issues from its user. We will not talk about the authority coming from the government because many of us here will not agree of them to interfere in the system because they can just ruin the anonymity by conducting KYC and other preventive measures. So, what I am seeing is the lack of addressing problems from the founder of the crypto. After they implemented the system they will just say that system is good and ready to go and if you as a user will get mistake then that is your problem and your fault. No one had force you to join in cryptocurrency and you must adapt to it. This is not good for those who wishes a better system.
There are ways to resolve on issue on protocol level without authority.
2. Miners service are decentralize.
Who would ever thought that they could get you a 1$ transaction of a fee which could be more than a thousand dollar's fee? There is something wrong and miners should be held liable into this by only limiting the transaction fee to be deducted not more than the transacted amount. They are abusing due to the fact that their service is in demand especially the bullish trend of bitcoin.
Transaction fee rate is based on demand and supply, you can set low fees at risks of waiting longer for the transaction got confirmed.
Transaction fee itself is exist to prevent spamming transaction.
3. The abuse may be only happening and will be resolve between both parties. Same thought about in number 1 but this talk about resolution between both parties and not about the lack of authority from the founder. A certain user could mistakenly send high amount in the transaction without checking it and will be requested for a refund. The other party could deny and there us nothing you could do because it was your fault and no one can help you.
It's user mistake, even on centralized service refund could took long time, cost you refund fee or the authority simply reject your refund request.
4. Complete decentralize platform may gone wrong.
Again, there is no perfect system and if there will be errors that will going to take place expect that you can no approach any technical team to resolve the issue. Reminders that there are no technical team to review in that errors but only the forum provided.
If you mean error on protocol level, decentralized system could upgrade their network to fix error.