Centralized doesn't always mean bad.
Centralized coin being sold as decentralized is bad though.
But it is still enjoying the highest popularity just for being the pioneer of the cryptocurrency market.
I disagree because bitcoin wasn't the first, there were other projects before bitcoin attempting to create something like it but failed. Bitcoin succeeded after their failure and it is successful because it works as it is supposed to not because it was the "pioneer".
Bitcoin transactions are slow. it doesn't have smart contract functionality. The block size is small and that's why we are seeing the requirement of having Segwit and LN sorts of addons. To be honest, no cryptocurrency is flawless.
You are confusing limitations with flaws and some of the things you mentions aren't even limitations.
* Bitcoin transactions are the fastest in the world, you are just ignoring the fact that 1 confirmation doesn't mean the same thing in bitcoin and other cryptocurrencies. Some altcoins that are advertised as "fast" require tens of thousands of confirmation (taking weeks) to reach the same level of security as 1 confirmation in bitcoin network. Not to mention that some of them don't have immutable blockchains (eg. ETH and BCH) so they can never be considered safe regardless of how many confirmation your transaction gets.
* Bitcoin does have smart contracts, every single transaction is using it and it is called "scripts". It just doesn't have certain characteristics like "turing completeness" which is a good thing.
* The only valid limitation (not flaw) is the limited block space which is inherited by all blockchain based cryptocurrencies.
Just because some cryptos are somewhat centralized, doesn't mean they are worthless.
I would be fine as long as they are honest about it, but they aren't which makes them fraudulent.
Keeping our minds open will only pave way for more innovation in crypto market and that's good in long run!
Fingers crossed but so far I only see small innovation in small insignificant altcoins that die because someone is pumping another "top 10" altcoin and people care about making profit more than seeing innovation.