Keep in mind that the holidays (Holy Days) came in a variety of forms and all were requirements, not optional. And has been established, the penalties of the OT were very stiff. So as to the Death Penalty as a stiff punishment, that is a whole nuther ball of wax and I think it is addressed somewhere around here, if not I'll take the time to hit that one up. So to say: "huge penalty = not made for us" isn't true. The Feast holidays were also mandatory and had stiff penalties for not following them, including death penalty and exile from the people. And ALL the feast holidays were given similar wording of "devotion to God, make preparations, etc" and they are obvious even to the modern reader of being more "fun" type stuff, such as setting up tents, eating rich foods, reclining to eat, blessing others, etc.
Okay, I mean from a certain perspective "bored and hungry". For some people, eating leftovers and studying/meditating all day would be a horrible day, even if you didn't have to do your daily chores.
As I reread my point I think I will need to touch a bit more on the death penalty thing.
The quick answer:
When we sin, we die, period. It destroys a part of us and creates difficulties in our relationships with others. The OT penalties were so stiff as a real reminder that evil spreads rapidly and can cause the death of the community as a whole if left unchecked. Whether this is fair to the modern mindset is a point of huge debate. Look at the state of the death penalty even in murder cases these days.

