I'm not sure I buy that - you're only likely to find out it was a bad idea after the takeover, because the deal is deliberately opaque, early investors get special rights, it may only be for a small part of the private company's value, and the private company has not usually published all the data required of a public company.
There are very good reasons IPOs require all sorts of public documentation and due diligence. All that regulation which SPACs attempt to side-step is there because of previous scams run in just the same style as SPACs.
They are reminiscent of the weird companies formed during the South Sea Bubble e.g. A company for carrying on an undertaking of great advantage but no-one to know what it is