I have finished all MGS' as well other than the side stuff which is non-canon, and have but didn't finish Rising either. Anyways, I personally enjoyed Peace Walker, and the managing of soldiers didn't bother me in Peace Walker (I didn't love it, but it didn't bother me that much), it was a huge turn off to me in Portable Ops though. The one thing I disliked most about Peace Walker was, what I guess people consider the RPG element, which was upgrading your weapons.
The weapons upgrade wasn't bad in and of itself, but just how long it took you to upgrade them really padded out the length longer than the game actually needed to be so it felt grindy. One can argue that you should just play it cooperatively, but I never did that, nor did I ever want to. Something I've heard people say is that Peace Walker is less important than the other ones, and that's actually far from the truth, but yeah, I can understand some not wanting to get through it, it takes time to really get the hang of it and enjoy it.