How important are 'attachment styles' in modern psychotherapy?

Hello,

This one is for active and seasoned therapists.

I've been looking into some literature on relationships lately. Specifically into the (very limited) material about consensual non-monogany (poly). I read the book "polysecure" by Jessica Fern.

The first half of it goes deep into the theory of attachment trying to explain how the relationship to caregivers as children can determine the way adults form attachments in romantic relationships. It uses these ideas to group people according to 'attachment styles' that explain their relationship dynamics. The theoretical foundation is based on work by John Bowlby and Mary Ainsworth. The theory seems appealing but sometimes rubs me the wrong way with how deterministic and 'Bold strokes' it is.

My question is: is this theory something that has a lot of significance in modern psychotherapy? Is it common for therapists to look at the childhood situation to determine a clients attachment style and adjust therapy accordingly.

With pop psychology books like this it is sometimes hard to determine weather the theoretical ideas are foundational and used in practice or niche and a personal interest of the author.