I spent loads of time (most of my free time really) with my parents when I was a teen and I was always nice to them and never did anything that would offend.
It was because they burdened me - I felt responsible for their emotions and wellbeing. I felt like (and was) my mum's only friend and confidante. She didn't know anything real about me and thought I was perfect and always happy.
Actually, this dynamic really set me back as a young adult, I struggled with some mental health problems and felt unable to confide in anyone, always presenting a cheerful self, not really having any deep friendships etc. I have since had to go through a bit of an identity crisis triggered partly by having my own children - and have come to reflect a lot on how I was parented. I still love my parents, the relationship is better now and they are good grandparents - but I still feel like we'll never be authentically close because they don't see the real me and on a level, particularly with my mum, her emotions just come first.
Obviously this is just my experience/ perspective and might not generalise.
However, overall I think that your teenage daughters (safely) pulling away from you and being to an extent, inconsiderate of you, is developmentally normal and shows that you have done a good job raising them to be healthy, independent adults. Whilst this time must be difficult and sad for you, I hope that you can take comfort in that. As others have said I think that in time they will come back to being close with you again, and you will then reap the benefits of a truly authentic and respectful relationship. I second others' advice to think about what you can achieve or explore with your new found freedom!