Yes it is. The bags get taken out twice a week and placed in and exterior shed until its weekly collection. At no point do the old bas come through the house.

Take the trash out every day.

We take our trash out every day. Any throw away raw meat scraps or bones are put in a zip lock bag.

Maggots come from flies. Do you see flies in the area?

That's the weirdest part of it all. I haven't seen any flies for weeks now in the house

Can you move the bin to another location in the kitchen for a while? There must be some eggs somewhere, or some flies in the area, or you wouldn’t keep getting the maggots.

Cleaning won't do a thing--you have to find and remove the food source.
That food source isn't crumbs; it's something bigger. You're finding
maggots and pupae because they leave their food source when they
are ready to pupate. But that's not where they grew up. They don't go
very far of course, but the eggs were laid in their food and that is
where they spent their maggothood, NOT on your nice clean floor.

Take the trash out every day until you break the cycle. But, you should confirm it's the trash that is the source.

Move the bin to a different location and see if new maggots move along with it. If they keep showing up in the original location, it's not the trash.

While we're at it, what kind of flies? Or at least what size? And what's the climate like/what part of the world? The life cycle speed increases as temperature does.

Is it an apartment/attached house/condo? What is below the maggot spot? And if against a wall, what's on the other side?

It might not be you! You might be able to blame that guy next door!

You've made a good start and gotten great advice. My advice is to take everything out of your cabinets. Remove any shelf paper. Vacuum the cabinets' insides and then wash the shelves with hot soapy water. Put any unsealable bags and open boxes in ziploc bags. Don't put food items back in the cabinets just yet, leave them out on a table or counter for a week. Check the bags every day to see if there are new bugs visible.

You can also move the fridge out and clean underneath it.

Pheromone-baited pantry moth traps work very well if that's what you happen to have.

If you take photos of the larvae and pupae, you may get some comments identifying them.

It sounds as though you may have some flies inside the cabinetry that are reproducing hence the maggots. See if you can take the entire receptacle out and spry with fly spray and let it dry for a day or so. I would do a couple of treatments and then clean with Clorox wipes on the plastic material only. Do a test spot for the spray in case it causes changes in color in the interior wood surface of the cabinet. Hopefully that helps.