RandomX has nothing to do with centralization. Exact opposite in fact for mining. How many people own CPUs vs ASICs? The ubiquity can't be beat.
If you argue that it is easier to attack using CPUs, that is a different argument. But it is also easier to bring more CPUs online from honest actors to defend or pushback against an attack as well. Exact opposite for ASICs.
Only two pools, AntPool and Foundry, make up more than 55% of the mining hashpower alone. Those miners are using their nodes. So Bitcoin has it's own centralization issues to work on as well.