Engagement is a funny metric. For a lot of businesses it's correlated with revenue but from a user point of view, it may be the opposite of what we want. Do you want a product that tries to keep you using it for a long period of time or one that lets you get in and out quickly?

As far as ads go, I'm fine with them philosophically. I'll pay to remove them when I can but I have no moral objection to them. I do object to tracking though and that's why I use an ad blocker.