DD (21) and I have always had a really strong relationship, we are really close, maybe because we have only had each other - I raised her a single parent for most of her life, so its just been the two of us.
She has a busy social life but she always makes time for me -lots of coffee dates, she always invites me around for dinner at her flat, we had a nice holiday together at the start of the year.
I was a pretty relaxed parent but she was a fairly easy going teen, I didn't let her get away with murder but so long as she followed my two golden rules 1) she did her homework 2) told me where she was and what time she would be back.
I definitely picked my battles, she was well behaved, streetwise and kept on top of homework, plus had a part time job and played sport so I let stuff slide - I didn't nag on school uniform (god knows how she didn't get that many detention for breaking uniform code constantly), she could wear make up / piercings, she was allowed to drink when she started 6th Form, I didn't set boundaries on screen time etc.
It probably helps that it was only me making those decisions, I can't imagine ex agreeing to any of those...