As for the "lack of explanation" about divine protections and skills, I don't really know what ManosP1 was talking about, it seems like they maybe just didn't read enough chapters to get to the explanation. I will say, the manga doesn't give an ELI5 explanation like a lot of other fantasy manga. However, it still makes it pretty clear how things work: a "divine protection" is one's specific role in life, as chosen by the gods. For example, Red's divine protection is "guide," meaning it was/is his job to protect lower-level heroes until they are strong enough to protect themselves. As for skills, the way they work is much like a video game, in that you can increase a skill whenever you level up; "common skills," are just that, skills that anyone can level up. These include mundane things like cooking and fishing (though only to an extent). "Intermediate skills" are similar in that anyone can acquire them but they usually are only necessary for adventurers or people with a higher level, such as "first aid" or "brewing." "Advanced skills," on the other hand, are skills only available to certain roles/divine protections. For example, someone with the divine protection "chef" would be able to increase their cooking skills beyond just the common level. As well, someone that is a "hero" role would have powerful swordsmanship/magic-based skills available to them.
The reason Red sees himself as weak is that he has no advanced skills to choose from (his divine protection of "guide" doesn't offer any) which means he has a limit to how helpful he can be, unlike his sister or the other adventurers who can continue to grow in power indefinitely. Especially since he was in the most powerful adventuring party in the world, he reached a point where he felt he was no longer needed and was only a burden. However, what this story tries to show us that even if his abilities aren't god-tier when it comes to combat or magic, he is still heroic because he is kind and caring towards those around him. As well, though he may not have any advanced skills, his experiences adventuring and his smart-thinking ( to combine the common/intermediate skills he does have) show just how versatile/helpful he actually is.
Overall, I recommend this manga to those who like realistic, straight-forward romance that doesn't beat around the bush, drown you in ecchi, or rush into things. However, I would not recommend this to anyone who wants another power-fantasy, harem manga where the OP hero just obliterates everything in his path and somehow attracts people to him without having done anything to deserve it.
