Bitcoin is just a word, what the majority chooses to call Bitcoin will be Bitcoin, all the hashrate and financial influence in the world won't help you there.
yeah, you can call your dog Bitcoin, but this fact don't make your dog real bitcoin.
Using an online wallet is completely defeating the purpose of Bitcoin in the first place. When the price rises high enough all those users will either go back to the old fiat system or use Bitcoin as intended and have the benefits of cryptocurrency. If they leave, they are not Bitcoin users anymore and if they stay they will care about the block size and all the other issues.
Yes, yes, YES!! This is real problem. People wants Dollar/euro/rur profit, they don't interested in Bitcoin as a payment system or system which gives your freedom.
That is exactly why Bitcoin was created in the first place and is now taking over the fiat system. Because sooner or later, people don't won't to be controlled by the few anymore, they want freedom.
They already have enough freedom. In Europe, USA and other high rate countries.
All you talk about is Google,Coinbase,Gemini, all these corporations. Even Google, as big as it is, will eventually die and it will be taken over by decentralization. They will all die out. They are just a place holder as a simple quick solution to earn some money for their founders until the real solution comes in.
Dreams

Decentralization could take away authority, but not corporations.