Focus on developer tools
I sometimes think that Mozilla should focus being the best browser for web developers. Perhaps spend a few major releases in a row with 90% of the changes focussing on the web developer features. The tools that help webdevelopers do their job such as optimisation and debugging.
It may seem odd but I think it’s strategically smart as it makes web developers focus on making stuff work on Firefox and then sort out the odd stuff where Chrome (and its engine clone Edge) deviates.
For the health of the web that is a much more desirable scenario than the one we’re currently headed where webdevelopers design for Chrome only and ignore other browsers.