I do apologize for the late reply, and you're probably the only person who'll see this, but I'll give some of my thoughts anyways.
I think these missions are really cool. I enjoy full team challenge missions; I find them a lot of fun. I do have friends to do them with (in fact, I hate playing League solo queue - there's a reason I'm not in a high ranked league - so I only ever play when friends are around anyways).
I can see the other people's point, though, and I can understand the frustration from solo queue players. In my opinion, I think these missions are a great thing, but the rewards should be minor and not necessary to get the best event rewards. (i.e. you shouldn't have to complete a 5 man challenge mode to get the Ashe chroma and border if you wanted them in this event.)
That way they can be around for those of us who like doing them, with some small incentive for completing them, but they're ignorable for people who can't or don't want to.
Your comparison is a bit faulty. Riot isn't hitting people with sticks. No one likes being hit with sticks. This is more like Riot handing out candy that's in a strange flavor that only some people like.