If there are a majority of my target niche companies that literally don't know my type of software exists, and it could help them, but having physical door to door salespeople would make the software more expensive than they'd be able to pay, what approach do you recommend?

For you? I'd say do whatever you think best. It's an imperfect world we're all trying to survive in. I mean, as ominvores, we only survive through the destruction of other life, which is kinda horrific. But it's not like there are great alternative choices. Meat is murder, but I'm still having ribs for dinner.

As I said, I don't think door-to-door sales is good either; it's just that the time cost is symmetric, so it's less abuseable. But it's still bothering people to get paid.

In a better world, people would find out what they need to know without manipulation. And that better world is partly here. If I know I need to buy a thing, I'll look at things like Wirecutter and Consumer Reports to get unbiased evaluations of things. If I know I have a problem but don't know a solution, I'll search, I'll read up, I'll consult forums like this one. And of course I read broadly so I can become aware of problems I don't realize I have yet.

But it's only partly here. So if that's not enough for you, well, do what you have to. My issue here isn't with people doing what it takes to get by. It's with people insisting we all pretend that there are no moral compromises involved.