How to care less about teaching?
Superficial solution: Control your behavior with a time budget

Sit down and set priorities for your current life. Your research is probably more important in the long run than the joy you get out of teaching. If you agree with this, set a time budget for each area. E.g. assign 70% of your time for your research and 30% for teaching. Plan your teaching preparation accordingly. If according to this budget you can only spare 2 hours a day for the teaching but making custom exercises takes more, use prepared exercises. Also do not offer additional hours if your daily budget does not allow that. You can use a time tracker software. You may also try to do x hours of research related activities first before you "allow" yourself to spend time on teaching.

In-depth solution: You are not responsible for everyone and nobody will pay you back

It is admirable that you sacrifice yourself for other students. I also had mixed experiences with other tutors and when I became a tutor myself I wanted to do it better and often stayed one or two hours longer to make sure everyone understood the material. It felt like I had an effect on the world and could show them that there are people who care about them. It is a great feeling, BUT...

...will these students help you with your research? Will they give part of their earnings to you when they start working as a thank you for what you have gave them? Probably not. There will be no additional compensation for your excessive commitment. Nobody takes care of you, but you. This is sad, I know, but this is the hard cold reality. Few people care about you, unless they get something out of you. 

Additionally the apathy of the tutors is the shared responsibility of the faculty, not yours alone. Don't let your ideals guilt you into feeling responsible for it.

You are not a trash teacher if you do less

The other teachers might have realized the previous point. Sure some just don't care and are trash teachers but maybe some of them, in their hearts, are just as idealistic as you but realized that spending time on their research or with their families is more important for their life and happiness. They are not ascetic monks that devoted their whole life to the "holy cause of teaching". If you realize that they are not bad teachers but just have created boundaries and a healthy work-life balance you will not be afraid to become one of them because you will not be afraid to be seen as someone who does not care about students but just someone who also has limited his working hours to a healthy pensum.

Make small steps to improve your universities teaching standards

Identify the most hindering problem with the easiest solution. Try to focus on one at a time. I don't know how your department works, but maybe you can mention this in a weekly meeting or talk to the head. Unless you are the head of department you most likely can't change the department on your own, small steps is all you can do.

Think about a teaching career

Not sure if this already crossed your mind but would you consider a career in teaching? It may suit your passion, although it might be depressing if this becomes your profession and you are stuck in a apathetic institution that does not value your dedication.