Is it considered weak to apologize for ones role in a relationship?

I was with this girl and she broke up with me over text. We dated for 9 months, she was very amicable regarding the breakup and even offered to meet me the same day. She was very distraught that I didn’t put in effort into the relationship, never defined it, never called her, etc. She said she felt like I used her and that she knows her worth, that was before she blocked me.

I was wondering if it would have been better to approach the breakup text in as few words as possible, even if the main reason for the breakup was my fault