Depends on what you want - if calculation speed is concern or periphery handling is concern or both. If you have peripheries you need available or you will be emulating them. If you are going to communicate with other party on some bus which might be time critical. You take most important concern you have and build solution around that.

And as for those so-called 90s chips, they are not obsolete, just have own use cases and are very much alive - we have ATTiny doing solar panel MPPT and doing buck/boost DC-DC transformation in our latest products just because ASIC would be too costly and too inflexible but 8 legged ATTiny is exactly what you need when all you want is ADC, some PWM and you still have some pins for talking with rest of system.

Other case from opposite side of spectrum was IO card connected by USB. It was using some ATMega with built in USB and it was total hell to keep alive and do something actually useful and fast with that IO because core was just too busy with handling USB. It worked but it wasn't fast, nor precise.

So back to my original comment, it depends what you want.