Heroku's suggestion: "modernize and optimize your web stack."

I don't have any experience with Ruby web stacks so I'm curious if this is actually an option for you guys? What would it take to do that? Would the performance increase on Heroku be worth it?

It also seems like if you wanted to self host you would probably need to do those same improvements, right?

Please don't take my comment the wrong way, I'm not trying to say Heroku is somehow excused from their mistakes here. I'm just trying to understand that suggestion from Heroku.