In a truly competitive market with many equal(-ish) players, then the software with things people hate most, like adtech, would lose out to those that ones that provide what people want the most, like speed/stability/usability.

Do you think so? The problem with adtech is that it subsidizes the products by trading a margin of annoyance for extra revenue, allowing lower consumer prices. I would argue that the current market already does have many evenly matched players, and they naturally gravitate toward an equilibrium where they have as many revenue-bearing annoying features as the market will bear. As an example of a correction I recall the old days of popover and popunder windows that were worse than today's run of the mill site.

This is why it's hard to find an affordable dumb modern TV. They do exist, but they are pricy and made in small volumes. The market has spoken loud and clear.