I was in your position for a while. Though my disinterest was caused by depression and anxiety causing me to do nothing at all, much less play with my rats. I had eight rats at the time and ended up rehoming three of them, mostly because those three were more than I could handle and I felt little to no attachment to them at that point. I hardly was giving any attention to my rats, but those three were especially neglected for reasons too long to explain here.
My suggestion to you is to look at what is important in your life. My rats were important to me, so I forced myself to take care of them even when I didn't want to. I'm glad I did because I was able to work through it and now I enjoy my rats more than ever after I made some life changes.
However, if you can't bring yourself to give your rats the love and attention they need, I highly advise you to consider rehoming. They need love, care, and companionship and if you cannot bring yourself to give that to them, they may be better with someone else. I know it's a hard thing to think about, but I hope you will use that thought as encouragement to spend time with your rats.
Which is preferable to you? Them sitting in their cage with no human interaction, them going to someone who will provide them with plenty of love and interaction, or you spending time with them and giving them the love and interaction yourself? Think on those possibilities and then choose what your priority is and do what you think is best for your rats.
I do have suggestions of things to try to get interested again. Have you tried teaching them tricks? Setting up a maze or an obstacle course for them to navigate? Though I haven't kept up with it, teaching Pooka and Anya tricks REALLY helped me find enjoyment in them. Even my ailing girl Eevee, who has since passed, got in on the action, so age has nothing to do with trick learning ability and it could be something as simple as following your hand, which is what I started with. Going through hoops is super easy to teach as well.
I'm sure you'll end up doing what is best for your rats. You clearly do love them.

Everyone goes through hard times. I'm really not trying to be harsh by mentioning rehoming. I just know the idea of rehoming my girls was the kick in the behind I needed to work harder at taking care of them, because I certainly didn't want anyone else doing it. lol.
Best of luck to you and your ratties. I'm sure everything will work out right in the end. ^_^