It would be so easy if there was a one size fits all advice. We humans all go in to it with a preconceived idea of what we want. We have a vision of ourselves riding the bike we saw XX riding. We research the materials and brands. Get taken in by ad copy. Unfortunately the bike we often really need may seem pretty dorky. And when we don't impress everyone on the first ride, it must be the bike.

That is where the idea of a beginners bike comes in. Make your mistakes on a cheap bike, and don't upgrade, only change things that change the fit. And finally, as you gain fitness, figure it out or find you can't get there from here, start over.

But cheap bikes are slow, right?
https://m.youtube.com/watch?v=BHOJ2814J9Q