Example: When Jira was the new kid it was all snazzy and sleek and interesting. Over the last few years a lot of alternatives have appeared. Although Atlassian has made some changes, they can't just bring in what makes those products different unless they write a whole new product, and large companies can't make new products.
Currently I think we're at or just past a high point. The current lineup of Jira alternatives will probably wittle down, the best ones will get bought, made part of some enterprise lineup, that way of working becomes a standard, they'll get big and bloated and unable to innovate. The cycle will get to a low point and then we'll see another explosion of alternatives.
And that's just one niche.
It's harder to find the business potential because the opportunities are much more closely coupled to optimizing specific processes in specific industries. But if you can find the right niche, the business opportunities are there.
The "current" use of the word implies VC capital. As in "I joined a startup and we raised..."
However in the past it referred to literally "starting a business". Someone sees a gap in the market, builds a product, and looks to fill that gap one customer at a time. Since there is no incoming capital, it has to be revenue positive, well enough for the owners to survive.
This sort of business is (somewhat perjorativly) called a "life style" business. In that it provides salaries to some number of people, and provides a (good?) living.
The reasons for starting such a business are numerous, and while maybe some do with the goal of being mega-rich, in reality the successful ones end up being merely "rich".
But there are a _lot_ of upsides other than money. I'll offer a few from personal experience, but really they offer any goal you like.
A) freedom to work on what you want, when you want, where you want, how you want. Yes, of course you are constrained by actually delivering (or you don't get paid) but the mechanics of delivering are up to you.
B) job security. It takes time to get to this point, but once a business is profitable the owner has a job for life. (he is literally the last person to get laid off) [1]
C) a lack of corporate bullshit. No endless layers of managers. No endless meetings. If you need a new PC you go buy a new PC. (equally true, if you report directly to the owner, decisions get made quickly. If you need a new PC you only have to convince one person.)
D) while on the topic, being employed by a small business has huge benefits as well, but to need to move the income needle for the job security.
I could go on but I think you get the point.
[1] ironically when getting person credit, like a mortgage, ticking "self employed" leads me to a lower credit score, despite the fact that 40-odd people get laid off before I do :)
[2] about 5% of new (bootstrapped) businesses make it to 10 years old. I'm not suggesting this route is easy, but it is desirable.
Financially, it's the exact opposite of a problem; it's too profitable. There will always be big market for companies that manage to lock up an audience within its walls.
I bet there are lots of sectors out there that could be totally disrupted or made more efficient if they got attention from high-caliber developers and UX folks.