Well, what's a tool? I would say:
1. It solves a problem. Doesn't have to be a completely unsolved problem, can just be a new solution. Or even just new packaging on an old solution. But it needs to solve some kind of problem.
2. It's trustworthy. Some people get a tool to suite their own process. But the majority, from anecdotal evidence, will adopt the tool's process. There's this idea that "these guys know how to do invoicing so I don't have to think about invoicing if I use their invoicing tool".
3. It's known. A bit philosophical, but if something exists that nobody _knows_ solves a problem they might not even know they have, how much of a useful tool is it, really?
DropBox is an interesting example. It wasn't exactly a major scientific breakthrough, and a lot of people asked "why don't people just use FTP?". If you focus on (1), DropBox looked close to pointless. But what they did is nail (2) and (3).
Now, if you subscribe to the hype, you might argue (1) and (2) will soon be covered. AI will magically solve your problem and be a universal domain expert telling you what to do, so you don't have to think about it. You might also argue that it will magically solve (3), with stuff like Gemini Live kinda watching you all day and constantly going "let me tell you how to do that" or "let me do that for you".
Seems unlikely to me. Not impossible, most things I can think of are theoretically possible. Just unlikely. And if you think even just _one_ of those three aspects can't be fully automated in the near future, there's still plenty of opportunity left to differentiate in that area.
I think generative AI does unlock a new generation of startups, because it's genuinely new technologies that we can find at least some valuable use cases for. And an army of startups tends to be better at quickly exploring a new solution space than a few big incumbents. So in that sense, it is similar to smartphones, which also brought a new solution space, and with it, startups.