That's...just not true at all.
Stop cancelling from 3C already (and don't abuse 214DA on people who likes to mash 2/5A unless you've taught them to not do it) and instead mix up which normals you cancel from.
If anything 214DA is way too good since it's always + on block (+2 lv 1, +8 lv 2) and it's Hazama's fastest overhead (19f, 6A is 22f).
214DB is kinda...meh, like, it's alright to use at times, but for most situations you'd use 214DB for (AA/occasional reversal), there are better stuff to use.
Of course this does not mean 'spam dat ressenga', but saying it's bad just makes no sense.
Even 214DC is pretty good, it has decent pushback and it's relatively safe if not IB'd (or even if IB'd maybe, spacing dependant).
Hazama's mix up are all about command throw and stance high/low, just don't be predictable and do stance off 3C or stuff like that.
Randomly doing stance off 3C is alright, but I'd say the best option after 3C is 236D, there's no point in not doing that (I think, it should not be punishable even if IB'd, unless, idk, Tager can sledge through it or something, but I really doubt that), of course doing 3C>236D puts you kind of far away from your opponent, which is not that good in a few MUs.