Financial literacy is a very important skill. Yes, startups are complicated. To be an informed employee you need to deeply understand how stock options work, you need to deeply understand how startup financing works, and it wouldn't hurt to have a general understanding of business. And look, if you just want to be a software engineer, then you don't have to learn these things, but then you can't complain if you get screwed. Or take a job at a publicly traded company and use the stock price as a proxy for how the company is doing.
And as for the availability of the documents and financial information, the main ones you care about are: revenue, expenses, total burn and cash in the bank. Any company that will not reveal those is being shady, full stop. These figures should be so top of mind the CEO or CFO should know them off hand without even having the look. A good company will share all of these with the full company every month or quarter, because they are really important indicators of how the company is doing and what the overall strategy should be.
You don't need a lawyer. You are not auditing the company, you are just getting a sense for the company's trajectory. Your job is actually really easy. If things are going well that is normally obvious. Revenue going up. Burn going down. Fundraising rounds at higher valuations. If these things aren't happening or you suspect something shady is going on, leave! You don't need to break the case, just get a better job at another company that is doing better.