Toothbrush UX is the same today as it was when we were hunter gatherers: use an abrasive tool to ablate plaque from the teeth and gums without removing enamel
https://www.youtube.com/watch?v=zMuTG6fOMCg
The variety of form factors offered are the only difference
Yes, whittling down a stick is pretty much the same experience as using an electric toothbrush. Or those weird mouthguard things they have now.
I don't think most people would find this degree of reduction helpful.
As somebody who's tried using a miswak [0] teeth-cleaning twig out of curiosity, I can say with confidence it's not the same experience as using a modern toothbrush. It's capable of cleaning your teeth effectively, but it's slower and more difficult than a modern toothbrush. The angle of the bristles makes a huge difference. When the bristles face forward like with a teeth-cleaning twig your lips get in the the way a lot more. Sideways bristles are easier to use.
[0] https://en.wikipedia.org/wiki/Miswak