I realized that I have web-protection-overkill: Malwarebytes' protection, Firefox's built-in protection, and -- most of all -- my own micromanagement of browser permissions via user.js, umatrix, and ublock origin. I decided to see if my (already fast) browser was any faster after removing two layers of protection. The problem of Malwarebytes' inflexible notifications was soon apparent.
So far -- and this is as likely to be placebo as real -- my browsing experience feels faster. There's a pause between clicking a link and the moment that a page begins to load. The pause seems to be halved since I turned off Firefox Safe-Browsing and Malwarebytes' Web Protection. Browsing just feels a little snappier. I'll have to switch back after a few days or a week. Maybe repeat the process. I don't have a means of measurement.
For now, I'm relying on blocklists for known malware, malvertising, & tracking domains; filter lists to process content; umatrix to grant fine-grained permissions; and sites like urlvoid.com, virustotal.com, and mywot.com to aid those decisions. Maybe I'm being foolhardy. I don't know.