You realise how weird this sounds, right? Presumably you donate because you care about the Mozilla mission, and those ads are there because donations alone aren't enough, and relying purely on Google's money is also not a great strategy. What do you want them to do, invent money out of thin air?

And it's still Firefox: if you're upset enough to consider "migration to a different browser", why not instead get upset enough to just look up the pref that turns them off? Because that's the whole point of Firefox: you're still in control of your browser, and almost everything is yours to set to your liking, even if it's not in the normal options UI. Don't want those ads? Hit up about:config, turn them off, problem solved?

And in the mean time, Mozilla still needs your help, because breaking today's Chrome dominance by offering a better product (not just a competing one. People don't switch if the offering is more of the same) is orders of magnitudes more difficult than when they broke IE's dominance many decades ago.