the point is bitcoin being opensource means people can look at and change the code and given that, we can pretty much assume every aspect of bitcoin will be put under a microscope and there will always be factions that want this change or that. one of the weaknesses of bitcoin not being immutable code...
Are you trying to imply Bitcoin protocol and it's implementation should be closed source? I find it's ridiculous. Even Windows have to deal with people/company who reluctant to upgrade through WoW and LTSC.
mining centralization
Unfortunately Bitcoin miner not interested to use P2Pool[1] which development stopped on 2018[2]. Since Monero is mentioned here, i'd like to mention P2Pool for Monero is actively developed[3] with ~4.7% network hashrate[4].
[1]
http://p2pool.in/[2]
https://github.com/p2pool/p2pool[3]
https://github.com/SChernykh/p2pool/[4]
https://p2pool.io/#blocks