There are literally at least hundred thousand developers who have worked for 20+ years on financial systems - the industry employs a lot of them. If you're going to be storing money of other people, picking up a random such guy - even completely mediocre, boring one - would at least bring up the many issues that are taken for granted in 'that world' but nonobvious if you're not from the financial industry.
At least not if they are populted solely by young, hip developers. Those developers can probably build the system, but what they can't do is specify and validate the system. So, those young, hip developers need to at least spend some time talking to some experienced domain experts.
Or, you know, keep repeating every failure in the history of finance and banking that has led up to the industry practices and government regulations they are ignoring. Sure, you can likely find better solutions to some of those problems, but it would be better if you at least "anticipated" the well-known, obvious problems and solved them, rather than repeating them first.
Only with that mindset can one build a system that doesn't screw over every legit customer when it happens.
If you start a BTC exchange, write half of the initial code yourself, have access to the servers and own the company - then you should ask a simple question: could I myself steal funds undetected? If you're an investor, could the CEO/founder steal funds undetected? If the answer is yes, you have work to do.
There are some theft options by privileged people that can't be realistically prevented, but you can make sure that those scenarios would be detected within a day, and thus those privileged people simply wouldn't do it to avoid jail.
Then ask, how many of these things are true for bitcoin? Then perhaps ask, could I provide these things, and make money while doing so?
Writing bitcoin software should be like writing crypto: you aren't smart enough, so don't try.