Then OP would have to work on finding more time to spend with them, and a lot of other comments address possible ways to improve this.
Personally, when my partner complained about not spending enough time together, I increased the time I spent with her, and it didn't help alleviate the frustrations she was feeling. She thought that what mattered to her was Quality Time, but it was really hearing Words of Affirmation that was important (I see a similarity with users who say they want a particular feature, but really just want to solve a certain pain point). Only when we figured out how she feels maximally loved was I able to use the time I spent with her effectively.
Then it's quite possible that they spend time together but it's time spent in the same proximity but not spent fully engaged.
My partner and I used to have this exact issue (with me being the one who didn't feel like we had enough quality time). She would often retort "what are you talking about? We spend at least a couple hours together every day!" And I'd go and think about it, confirm that, yes, we would often spend the evening together on the couch, with both of us on our laptops working. And then I'd scratch my head, feel confused about the mix of contrasting thoughts going on in my head, and carry about my day feeling uncomfortable about it.
A while later, I came across 5LL and read through it pretty voraciously. It provided context that I'd never been able to put into words. Lately, we probably spend even less time in physical proximity than we did then, but we spend time together where we're both fully engaged and in the moment with each other. It doesn't take much for us to both feel pretty happy about things.
[tldr: quality can be much more important than quantity re: quality time]
Personally, when my partner complained about not spending enough time together, I increased the time I spent with her, and it didn't help alleviate the frustrations she was feeling. She thought that what mattered to her was Quality Time, but it was really hearing Words of Affirmation that was important (I see a similarity with users who say they want a particular feature, but really just want to solve a certain pain point). Only when we figured out how she feels maximally loved was I able to use the time I spent with her effectively.
I thought maybe OP could be in the same boat.