How are people realistically supposed to crate train in such small increments?

I’ve been struggling to crate train my new 6 month old puppy and I’m well informed on how to do it, i just don’t understand how it can be done in real life. My other dog is a rescue and never liked the crate, was fine without one and still is so I ditched the idea. So far the new pup absolutely hates it and I just don’t understand how I’m supposed to acclimate him to it in such small increments. Like they say to start with only seconds in the beginning, then work up to minutes then hours. Doing it at this dog‘s pace would take me a year to get to the only 3 hours he’ll be alone each day until my mom gets home from work after I leave for my job. I can’t not work for a year, what do people do?? I’m guessing most people don’t have as much trouble with crate training as I am. I understand some people have sitters which I’m doing right now until he hopefully improves, but I can’t do it forever. I can’t leave him alone in any sort of way until he’s crate trained because he’s exhibiting signs of separation anxiety and I haven’t even had him two weeks. He poops every time I leave even though he just went and is with someone else in the family. I’ve debated giving up on the crate if he doesn’t improve in a few weeks but I have no other way to keep him safe.