Still, there's some questions you'd want to ask that would be an immediate red flag but regardless of answer outcome you still want a job offer since you are interviewing multiple places in parallel and you don't know how picky you can be. You end up not asking those questions because they'd put your "culture fit" at risk. You can ask other questions and try to read between the lines but bottom line it's tough to know exactly what you're getting into no matter how much access you get.
Early this year I spent 3 or 4 months job searching for my next role and ended up not taking any of the 3 offers because something seemed off at all of them. After I got the offers the recruiters turned into used car salesmen which was also a different, terrible experience. So even if you do end up with the insight it can be a gigantic waste of time.
I've personally never experienced this sort of thing. It's entirely possible I'm a combination of lucky and privileged (eg I'm NT as far as I know). That aside, I feel like you need to determine what your values are and pursue lines of questioning along those. They should be things that are near deal-breakers.
I just don't really understand not asking a question whose answer is highly valuable to you because you're worried about getting red-flagged by the company. I also don't really get pursuing offers from companies you don't care about unless there are heavy job market pressures eg being a new grad/looking for your first job in the industry. Even then, the idea is to just get your first job, so your values are different than when you're more senior.
Recruiters can absolutely be awful. I've straight up ghosted multiple because they were unable to take "no" for an answer.
Early this year I spent 3 or 4 months job searching for my next role and ended up not taking any of the 3 offers because something seemed off at all of them. After I got the offers the recruiters turned into used car salesmen which was also a different, terrible experience. So even if you do end up with the insight it can be a gigantic waste of time.