Are we not supposed to tell our therapists everything?! I need advice on boundary setting with therapists...

I always thought therapy was the one place we could be completely transparent and honest... Over the last couple of years of bad experiences with therapists and referrals... I'm realizing I should treat therapists like an ordinary relationship where I don't tell the details of all my trauma or say all my thoughts everyday just because they are my therapist. It sounds like I'll have to build trust slowly and decide if I can really trust them before becoming very vulnerable. As Brene Brown said, people have to earn your vulnerability and you have to be careful where you share. I have this tendency to want to rush and heal so for me I thought let me rush the intimacy and share my life quickly so we can get down to business and do the work. I now see how doing this has led to retraumatization because they were not supportive or the right fit and led to manipulation and abuse. Ever since being abused by my last therapist, I don't even want to open up to therapists anymore.  I will have to really work on opening up safely and authentically by sharing a little and testing how they react before proceeding further and really listening to my gut and instincts on whether or not we are the right fit. I've also recently gotten referred from some therapists and scared them off after telling them right away I reported a therapist. It sounds like I'll also not be able to share that right away either... They may see me as suspicious like someone who keeps saying they have crazy ex girlfriends when first dating.. which sucks of course because you would think the one place to be completely transparent is therapy.

Any advice regarding setting boundaries and developing trust and intimacy in a therapeutic relationship?