According to you, is the increase in Bitcoin adoption a move toward centralization?
No, adoption will not create more centralization, they are independent variables. Nevertheless, many people will will opt to have custodial accounts, other will have a mix and others will opt to self-custody of the funds.
The important bits is that bitcoin will always give you the freedom to control your money (if that is what you wish). In a way it works like physical cash/coins, but fit for the digital world.