Bitcoin mining doesn't have to be for everyone(*), only the most efficient ones will keep up.
(*) If Bitcoin mining would have been for everybody, big changes would have been needed, see Monero.
This is a centralized approach to the issue though. Why not making available to anyone instead of excluding users from it?
I agree that mining is today a business which also tends to be centralized. I may be also tempted to propose "mining for everybody". But unfortunately the things are more complicated.
Clearly, "mining for everybody" means a war against ASICs and Bitcoin may get out quite badly hit from such a war.
The coins that can be mined by average Joe tend to have very low price.
"Mining by everybody" will face accusations that main miners are botnets.
Changing the algo from time to time to stay ahead of ASIC manufacturers means forks which can be seen as signs against stability.
So unfortunately there's no really better alternative to the current way the mining goes. We can just hope that mining businesses can survive in different countries so the mining stays "somewhat decentralized" in the future too.