Best not hold your breath. You are an old-school power user and 99.9% of users no longer know or care about any of the functionality you're talking about.
I don't have any specific retorts to your points other than pointing you to https://addons.mozilla.org/en-US/firefox/addon/textarea-cach... for a Lazarus replacement (although I thought Firefox does this by default, and I don't understand why you need an extension at all).
Thanks for the pointer to this extension. I'll check it out. One of the things Lazarus provided (at the cost of adding some effort in maintaining privacy) was to save the history of form fields across sites and across restarts. In my knowledge, Firefox allows saving text fields, but not text areas. Periodic saving and history were quite helpful especially when writing longer walls of text like on HN comments or posts on other platforms.
I don't have any specific retorts to your points other than pointing you to https://addons.mozilla.org/en-US/firefox/addon/textarea-cach... for a Lazarus replacement (although I thought Firefox does this by default, and I don't understand why you need an extension at all).