Revenue/Expenses/Net Assets
2013: $314m/$295m/$255m
2018: $450m/$451m/$524m
2021: $600m/$340m/$1,054m
(Note: "2017 was an outlier, due in part to changes in the search revenue deal that was negotiated that year." 2019 was also much higher than both 2018 and 2020 for some reason.)
2018 to 2021 also saw their revenue from "Subscription and advertising revenue"— Representing their Pocket, New Tab, and VPN efforts to diversify away from dependence on Google— Increase by over 900%, from $5m to $57m.
https://foundation.mozilla.org/en/who-we-are/public-records/
Seriously, Mozilla gets shat on all the time, presumably because they're one of the few sources of hope and therefore disappointment in an overall increasingly problematic Internet landscape, and I wish they would be bigger too, but they're doing fine all things considered.
Certainly I wouldn't say their problems are due to this particular apsect of their legal structure.
I think they get shat on all the time because of what you mentioned but also because they consistently fail to deliver a good browser experience for most of their still loyal users.
Most of the people I talk to who still use their product do so out of allegiance to the values of FOSS despite the dog-shit products they keep foisting upon us. You'd think we'd wise up several decades in by now.