Mozilla is an online advertising advocacy project. Just try suggesting to anyone from Mozilla the idea of web without ads. They will be 100% opposed, unwilling to even consider alternatives, as if they are being paid to defend this pro-advertising position. They are indeed being paid indirectly from the coffers of an advertising company.
"Free and open web" apparently means web open for advertising. The presence/absence of advertising on the web is a non-negotiable. Mozilla insists advertising is a must-have.
Why was the original internet free of ads before it went public. Are there more important uses for a computer network. ISPs privatised the financing for the network. We pay for internet. It is not free. Funding from advertising has never been a necessity.
But Mozilla argues advertising is 100% essential.