Wrong take. You don't need to build something better, you only need something good enough that matches what you actually need. Whether you build it or not and ditch the SaaS is more of an economic calculus.
Also, this isn't much about ditching the likes of Jira not even mentioning open source jira clones exists from decades.
This is more of ditching the kind of extremely-expensive-license that traps your own company and raises the price 5/10% every year. Like industrial ERP or CRM products that also require dedicated developers anyway and you spend hundreds of thousands if not millions for them. Very common, e.g. for inventory or warehouse management.
For this kind of software, and more, it makes sense to consider in-housing, especially when building prototypes with a handful of capable developers with AI can let you experiment.
I think that in the next decade the SaaS that will survive will be the evergreen office suite/teams, because you just won't get people out of powerpoint/excel/outlook, and it's cheap enough and products for which the moat is mostly tied to bureaucratic/legal issues (e.g. payrolls) and you just can't keep up with it.
The sheer volume of data, the need for real time consistency in store locations, yada yada means that bad early decisions bite hard down the road.
Lots of drudge work can be assisted by AI, especially if you need to do things like in ingest excel sheets or spit out reports, but I would run far away from anything vibe coded as hard as possible.
I rather use Excel. It's likely More robust and safer than the vibe coded app that could trigger data loss / incorrectness / issues any time.
One of my clients spends 500k+ on XXX licensing per year (for a 200M revenue company that's not peanuts), and on top of that has to employ 12 full time XXX developers (that command high figures just for their expertise on that software while providing very little productivity) and every single feature takes months to develop anyway. Talking about stuff like adding few fields to a csv output.
So the total cost of XXX is in the 2M/year range, and it keeps ballooning.
My (4 men) team already takes care of the entire warehouse management process except inventory, the only thing that XXX provides, we literally handle everything: picking, manufacturing, packaging, shipping phase and many others.
In any case, nobody has mentioned vibe coding.
I stated that a handful of good engineers with the aid of AI in a couple of months can provide a working prototype to evaluate. In our case it's about extending our software that already does everything, except inventory management.
When you spend 2M/year on a software (1% of your revenue), growing every year by 100/150k it makes sense to experiment building a solution in house.
Spending tons of money to get a janky, unreliable system of record, or finding out too late it is missing crucial auditing capabilities, or that it has Big Money bugs, on the other hand, is far worse, especially if you have investors asking what the hell you were thinking.
Your point about users not knowing what they wanted until after the fact is also painfully true. The hardest part about these systems is the people most likely to buy are the ones who have been doing it with a lot of human processes for years. Buying a SaaS or other third party product means having leverage to force them to change to more standard practices. Building in-house means that everyone will fight to high hell to make sure that their special snowflake way of doing things is accounted for and you end up in a worse spot as a result.
There's multiple people highly involved into maintaining the status quo which do everything to take any responsibility out of them.