Some thoughts:
Microsoft has a history of losing interest and/or abandoning products and projects. While Defender is currently a generally acceptable solution, the time may come when it is relegated to the back burner (or gets taken off the stove altogether). Be on the lookout for such a development.
Malwarebytes is worth paying for. It catches things in real time that Defender does not. Sometimes I'm surprised by a warning that pops up when clicking a link to what, for all intents and purposes, was a benign search that should have returned a non-toxic result—unlike our pastor's search for Turkish Delight (a CS Lewis reference), which did not return anything like he expected. A story for another day.
Finally, after years of using Macrium Free, I opted in to the paid version of it as well. It includes something called Image Guardian, which prevents malware or ransomware from overwriting or encrypting your backups (at least in theory). It also allows the mounting of an image as a virtual machine, something I didn't expect to use but it came in handy a year or so ago.
