I usually use a Filco Tenkeyless (Cherry Browns), and removing the usually-redundant numeric keypad brings the mouse a bit closer to my right hand, so a bit more comfortable and a little bit of space saved. But I can't see the benefit of going smaller ever outweighting the cost of re-learning to type. Adapting to laptop keyboards when used to full-size can be tricky enough...
It would be better to use the thumb more, and not rely on the pinky finger as much.
Compared to a standard keyboard, these small keyboards typically have more keys for the thumb to access. (e.g. the planck has 2-3 per thumb). And once esc/tab/enter/backspace are used by the thumb, you don't need to use the pinky for these.
One way to use the pinky finger even less: you'd probably move away from using the pinky for Ctrl/Win/Alt modifiers, and use home-row modifiers instead.
I do think "layering vs more keys" is a trade-off and not everyone will have the same preference. But I think the advantages to using fewer keys outweigh the downsides.
But I do think it's pretty neat there's so much to choose from. How many people are complaining about a truly compact smartphone in the size of the original iPhone SE for example? You can choose between "large", "very large", and "I used to have a TV that's small than this". I think it's pretty neat that all these options exist, silly as I personally may think some of them are.
Plus, I feel like TKL is better-supported by aftermarket keycap sets, if you care about having the correct row sculpt for a key.
And yes, I love having all numbers and symbols at my fingertips without moving my hands. I don’t type faster but I type more comfortably.
I also have the basic editing tools arranged logically so I can move/delete/select a character/word/line at a time, to the left/right. Again without moving my hands.