Wow, you are well advanced in age to be still doing this. At this stage, the teens should be relying on the mid 20s FIRST before they come to you to save them.
As someone said- adjust to adult-to-adult mindset with them and you will see a massive change. Go away for 2 weeks doing activities so they know mum won't respond until after 12 hours as she is out with no network. Trust me, that will be the making of them.
My double orphaned niece whom I have parental responsibility for, since she was 2 years and is now mid 20s. After she turned 21, I would even ask her how old she was- when she was making silly choices. Funnily, she also 'happily replied to my Q how old are you, saying 21, when she wanted to assert her independence. Anyway, it was her losing a phone she needed to study via wifi when covid hit and recklessly losing it within 1 month and my categorically refusing to buy her a new one, that she changed overall. She saved, and pleaded with her older working cousins whom I have also supported, when they were young, and now earn good money but selflessly spend it ALL on themselves, and bought her phone. I knew she had a new phone and took 2 years to ask how she afforded it, as I had forgotten about her losing it, but not me refusing to replace it. From then on, she thinks more independently, considering others and able to substantiate her requests which are now very reasonable. She came to me with 3 days to go before college started ( I kept asking her) and I again refused to give her money beyond fees and minimal spend money and she ran to her grand mother- to teach her to keep me up to speed and to stop asking for things at the last minute as she had been doing throughout sec school. So, she is learning slowly, but I have had to just refuse and she sorted herself out. I stopped the guilt on the account she is an orphan, one she hit 18 and more so after 21. You are not doing them any favours by remain their machine support- you are human.