There are a lot of "tech businesses" that are actually using pretty pedestrian tech. What they are _actually_ doing is business model innovation with an underlying tech platform. Often, that tech platform can be commodity or relatively simple tech. There are other startup propositions, though, where the tech _is_ the thing, and if you get the tech right, then some of those other things end up being secondary (not irrelevant, of course) just not primary. This is assuming that you really have punched a hole thru the door with some amazing deep tech breakthrough, which not every company is doing, contrary to what they may claim.
There is a YouTube video [0] (which goes back to 2019) that does a pretty good job of making this point. Well, much better than I can.
To be fair to your original point: you're right that marketing and sales are hard. I'm just adding the subtlety that there are some tech businesses where the tech is _also_ hard, and perhaps even harder.
[0]: https://www.youtube.com/watch?v=C1DlZWfI6rk&ab_channel=YComb...