Arduinos (ATmega/AVR) have been steadily declining in the hobby scene because ESP32's are just about the same price but include BT and WiFi. ATmega/AVR are still fine for PIC or STM32 minimalism, but it's clear that this sort of thing is the future with immense functionality included even in the simplest, cheapest devices because of the economies-of-scale of churning out 10B-100B's.
AVRs main benefit is the incredible I/O you get from them.
AVR EA has a 16x gain 12-bit ADC on it, for example. And AVR DB has 3x OpAmps on it for free.
There are also LUTs that operate at full clock speed on these AVRs these days. Handy for glue logic (AND / OR / XOR gates, kind of a mini-FPGA on a few pins).
AVR Dx has multi-viltage IO, though it's closer to dual power supply.
One port (PortC IIRC) is on a 2nd voltage rail. So you can have one voltage (probably 1.8V) where most of your logic runs, but some I/O can be truly 5V in/out and push/pull.
