How do you even define "substantially"... would you prefer bitcoin to be flopping between PoW to PoS to PoSv to DPoS every month? Would that make you happy by seeing lots of changes instead of import work like testing, cleaning up the code, and patching vulnerabilities that don't have the marketing prowess as some fancy new scheme?
Perhaps, bitcoins problem more has to do with perception than development? Perhaps the solution to these perception problems is people doing research before spreading FUD.
Well, I already emphasized what I consider to be substantial improvement, nothing of that calibre showed up for years now. Yeah, I'm not into Bitcoin development, but I do read crypto news from various sources and I'm active on Reddit and I definitely can't remember when I read something about some big improvement to Bitcoin. So you can assume I'm an average crypto-holder and my impression may be the impression of many.
Apart from anonymity which is very important, but not even considered for implementation, I see confirmation times are huge problem. Those are the core problems that need to be solved, I don't want to read about new fancy wallets in the subforums you suggested to be read. Core problems need to be solved and some logic new features to be implemented.
And I really have no interest in FUDing because I'm 100% crypto now, I just wanted to give my impression.
Confirmation times do not matter. As long as the person you are sending a TX to is able to connect to a super node (and they are able to rebroadcast a TX they receive) they should be able to accept a 0/unconfirmed TX with little chance of getting a double spend attack with small to medium sized transactions.
If you have a shorter confirmation time then you will have more orphaned blocks and longer orphaned chains. With bitcoin as it is now, you very rarely see an orphaned chain of more the one block, while with shitcoins with short confirmation times you will often see orphaned chains that have 20 and 30 minutes worth of confirmations