I disagree. Difficulty impacts profitability. Profitability is dependent on price paid for electricity. Cheap electricity isn’t centralized.
Discussion
What? This isn’t about cheap electricity either. This is about who controls block template generation. No matter how many miners are online, that is an issue.
Centralization isn’t a problem until it is … and I’m pretty confident that miners at scale aren’t going to put their profitability / future profitability at risk if the overall hashrate starts to consolidate too much with any one pool / template. They’ll move / diversify hashrate