I mean, it’s not great, but it’s also not the worst. You can also disable it. Chrome gets money by collecting your data to use for advertising purposes. Firefox doesn’t do that, so I don’t see much harm in them advertising some of their products a couple times a year. Even wikipedia advertises their own donation period, trying to encourage users to donate.

If it were a persistent banner, that would be different. But a one time closable window, that can also be disabled, is really not that terrible. Companies need money, after all.