I have been climbing trees while hunting for years. Never a stand, just find a fork and have a seat, might be six feet off the ground, might wind up twenty. I never used any sort of harness.
For some reason, this year I suddenly became deathly afraid of being in a tree without a harness. Not a clue why, just is.
I've always worn a harness but recently have been more conscious of possibly falling.
I cured the foot slip issue years ago by going to rapid rails which enclose the step. Yes, they can be a little noisy but I've always felt secure especially with muddy boots.