The Fusion Drive is a hell of a lot faster than a plain standalone HDD. There's nothing "embarrassing" about that. It works as advertised, and it's a great compromise that offers bulk HDD-based file storage and also a fast SSD-based workspace for active files.
I had this very vividly illustrated for me when I opened up a 2011 Mac Mini with a pokey HDD, added a modestly-sized SSD, and created a DIY Fusion Drive using the Core Storage features that were added to the OS a few years ago. The result: basically a new machine as far as responsiveness.
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It's "get it done now!!" thinking like this, ladies and gentlemen, that gets us half-baked features and security holes. Maybe you love playing games with your file system, but I'd sure as hell rather have APFS done right than done quick.