As long as you can disengage from "people input" - psychologically, that is - an Ni and Ti loop will automatically begin to navel-gaze a new foundation for relating into existence. We could say it's as simple as cultivating the perception of factors in place of relationships. Not caring less, but caring differently.
Pragmatically speaking, the right thing to do is ultimately a matter of benevolent intent and effect irrespective of the depth of feeling.
I have been unable to let go of the really intense desire to help certain others
Recently I had to let go of someone I cared the world about. It didn't take away my caring. I believe you can still care from afar. In fact, sometimes caring from afar might be the best way to make apparent the line between caring and interfering - or maybe "crutching" is a more appropriate word in your case?
As a bonus, if during your hands-a-little-off approach someone begins to
demand you bring your hands back on? The line between their gratitude and their entitlement too will make itself apparent.
I know it's not healthy, but it often gets to the point I feel it's my responsibility to be there for them
It helps to remember that it's never our responsibility to determine another's direction in life. We can help shape its pursuance through our involvement, but its actual course runs whether it's us involved or someone else or no one at all; forces beyond our full control are at work there, to an extent.
They will probably be ok.
What about you though?