RPi's toolchain situation is awful for beginners/hobbyists. CMake and non-manifest-versioned toolchains are a huge barrier to entry. I'd love to use the hardware but have given up multiple times because I'd rather spend my time writing code than wrestling with toolchain setup. And they won't support platformio which could make things massively easier for beginners to set up.

Arduino was around long before RP2040, therefore RP2040 shouldn’t exist because the niche was already filled.

As a hobby user, RP2040/2350 seems like the best to for beginners. As long as it's not battery powered.

I'm using the RP2040s with FreeRTOS for a hobby project. I think the Pico probe is a much better debugging story than buying a Blackmagic (or if you got the dough, a Segger), to debug the "modern" Arduinos. I have one of the Atmel programmers for the Uno R3/2560/Mega boards and that's nice.

But for people getting started, the ability to just plug in an Uno R3 and stack a motor controller shield on it, is pretty attractive. I like the Cytron break out boards for the Picos, but I still think the path from opening the box to working thing is still easiest with Arduino.

Once you know what you're doing, (and maybe that's when you realize you need a debugger), you move on to something else. And with the Pico I can spend the $800 on an O-scope instead of the Segger.