They haven't lost it. Their goal was to kickstart something and they succeeded beyond their wildest dreams. The space has moved - a usable computer now demands a lot more than the original Pi, and they realized that - this is why their tinkerer platform is the RP2040 family. The market is very healthy and the ESP32 family has a huge space.
What RPi brought was the idea that a platform with good software support would allow for a revolution in the space above the power of an Arduino.
I use one of those myself when I don’t want to carry dead weight.
Of course, I’d love if the OLPC project lived up to their promise, but that was the stretch goal.
If you need compute with a bit more horsepower, the myriad of NUCs or thin PCs exist. If you need both in a single board, then the myriad of other SBCs that aren't Raspberry Pi's...
The main reason it was/is the popular behemoth is not because of it's tinkerability, but because it got mainstream appeal and RaspianOS is polished enough for the average windows user to go "wow, neat."
THere is no "knock off pi", there are many many popular SBCs with the same performance at cheaper cost (O-Pi, arduino), not to mention the mini PC space (NUCS, ie intel asus.)
Things get more expensive with specific ADC needs/etc