Decentralisation is just at surface ,scratch a bit and you will see that as mining companies grow bigger and fewer, they can just drop out of mining pools. These people will have millions of computers and have a decent chance at getting the block rewards.
If a DIY home miner sets up a computer. His single computer need to statistically wait a million blocks before he can make anything. Even if mining that block can pay for all his costs, its such a gamble and more likely than not he will get bankrupt and his computer will become obsolete before he mines that block.
The market will push towards centralization because its more efficient.
The only reason why crypto is still profitable to mine now is because mining equipment is in short supply. Otherwise you will see these 4-6 month ROI times disappear. Everyone would be fighting until its like 1 year ROI. Only the people with the cheapest electricity and cheap bulk orders on equipment can play.