Are Abs/Core work useless?

Core work is not useless. It helps strengthen your back.

do hanging leg lifts, weighted ab exercises...planks are kinda worthless.

What makes you say that? I'm curious as I'm still developing my core workout.

I've eschewed traditional situps, crunches, oblique crunches, and bicycle crunches based on Stuart McGill's informed criticism that the back-and-forth flexing of the spine eventually wears it out like a credit card.

My routine includes planks and reverse crunches. Those are both high on ACE's list of most effective abs exercises. The reverse crunch seems to be applauded for improving posture. The main criticism I've heard of the plank is that there's no range of motion, although it's a common position, and you can do variations.

I'm especially interesting in spine-safe gymless exercises.

planks are just too easy, i never ever do planks and one day tried to see how long i could go, and i did 5 minutes. I also have no interest in doing 5+ minute planks. I just think planks are tooo beginner. sure there are some variations that make it much harder but i'm just not much of an endorser of static exercises, i prefer one's with frull range of movement and that have a positive and negative to it.

I think it just depends on your situation. I can do hanging leg raises all day but planks are challenging for me. I like planks because they actually teach you what having a tight core means when someone says, "hey, when you do this other thing, keep your core tight."

For me it's maintaining strength in the core. I have too high body fat % for a six pack look. I hit the age where I started getting a sore back all the time and actually threw it out a couple times. Then got serious about health and exercise and worked on strengthening my back. To maintain that balance I make sure and work on abs also each week. So for me it was more age than anything else