Mozilla Foundation has already expressed an interest in controlling speech within Firefox. It is not an option.
Indeed, the only way forward is w3m.
For some reason Firefox has horrendous issues on older devices. On my Win7 company-issued laptop a fresh window from a fresh FF install grabs 3.2 out of 4GB of RAM. On my phone (2GB RAM) it gets into a crash loop where trying to type into the address bar or load a new page crashes the browser. Data loss due to crashes is less frequent than when I was running Chrome, but spending 10 minutes every few days repeatedly restarting the browser is gradually getting me to move to Brave.
Something is wrong with your Win7 PC/Firefox. On my ancient Core 2 Duo, 4GB RAM, Windows 7 laptop I'm seeing ~400MB of RAM usage and a few percent CPU usage having a few bank and a few government websites open. Firefox version 107.0-64 bit.
Do you have an SSD on that machine?
Could it be an extension you installed?
As if Firefox is not funded by Google.
They've divorced themselves from Google funding in the past (and signed with Yahoo in the US, other search engines elsewhere) and likely could again.
Not to mention being paid by Google for a service and literally being Google are two very different things.