Jester David
Hero
It still is a failure of communication.
WotC certainly doesn't get to both eat the cake (here! Lots of cool items!) and have it still (why you didn't think the game could handle actually using the 100+ pages of magic items!? We just wrote them, if you use them that's on you!)
In other words WotC shouldn't get away with not taking responsibility for making a game that cannot handle it's constituent parts.
They do not say "don't use feats and magic items unless you're okay with all our adventures becoming way too easy" on the label. In fact, they say next to nothing, hoping that apologists like you will deflect and shift the blame away.
Many DMs fall into this "trap". The blame for this should squarely rest in the lap of the designers.
I don't see how it's a failure of communication. They state pretty clearly that magic items are not assumed or required.
And they tried the alternative where magic items are assumed for the math, and that didn't work out very well.
What would you have done instead? Remove magic items from the game entirely? Make magic items cosmetic or only provide non-combat bonuses?
It's easy to find fault, but proposing a working alternative is harder...