They don't want to renounce their royal titles as far as I'm aware. They still want to partake in royal duties "continuing to honour our duty to the Queen, the Commonwealth, and our patronages". I guess that I'm more cynical but it looks like to me that they want to redefine their roles and gain more freedom over duties and movement. Giving up taxpayer money is the trade they are looking to make for it.
Meghan's profile is massive now so the level of acting jobs she will get offered will be at a much higher level. Harry can earn hundreds of thousands a night doing speaking engagements, as you say. A 'Harry & Meghan' Insta account could earn them double digit millions a year. The economic possibilities for them are many and great. 'Financial independence' will not be an impressive achievement.
I don't blame them for this move, in fact I'd say it was a necessary part of the modernisation of the Royal family. Apparently William is going to cut off most of the Royals from taxpayer money when he gets the crown and Harry would have been one of those affected, again being cynical but it looks a good moment to beat him to the punch and gain control of a positive narrative. Again though, I don't blame them for wanting some relative peace in Canada in which to bring up their kid(s).