That is definitely not how I remember the feature phone era. The OS was an afterthought seemingly whipped together a couple months before the device hit the shelves and nothing was ever consistent even across recent models from the same manufacturer.

Back then the primary goal was checkboxes for the carrier to advertise and UI/UX was a distant second priority at most. Sometimes an advertised feature would just flat out be unusable (such as MP3 players), but good luck waiting for any kind of update because by then those developers had already been reassigned to the next handset model they promised to carriers.

Also, Samsung extensively customizes their OneUI fork of Android, with its own UI look and feel that evolves independently from Android based on their own priorities. Plus Samsung's Android maintains hundreds of features that either don't exist at all on AOSP/Pixels or later get folded into mainline Android.

(Including the little known killer app suite "Good Lock" available on Samsung's Galaxy store which gives power users an almost obscene amount of additional niche options and customizations that would give UX minimalist designers at Google or Apple a heart attack)

But despite how different Pixel vs. OneUI look and feel, I can use the exact same apps whether on a Pixel or Galaxy or $100 trash phone. Interoperability is very easy to take for granted and Android app ecosystem is (still) paradise compared to the lowest common denominator J2ME "app" era of the 2000s.