I think it's baffling that a) WotC designed the game with 6 different Saving Throws and b) they knew that half of them were useless when designing the game, because when they gave the Classes their Saving Throw proficiencies, they made it sure that all 12 of them got proficiency with one useful one (Dex, Con, or Wis) and one useless one (Str, Int, and Cha).
How . . . how do you do that? And why? If you're designing a system with 6 different types of Saving Throws, make them all useful! If you know that half of them are useless, get rid of that half!
Overall, I like 5e. But there are some really baffling design decisions that always make me wonder what was going through the minds of the game designers when they were writing them. (Making the Versatile weapon trait when there's absolutely no reason to ever use it, creating True Strike, which is worse than just attacking twice, and not giving Divination Wizards access to the spell divination, just to name a few.)