I am saying if you right now attempt to play the playtest rules along with your existing PCs, they will immediately need a house rule to make some of them work.
Here's some more.
You have a Variant Human or Custom Lineage feat that is a half-feat with a bonus to an ability score so you could start with an 18 in that stat at first level. Not compatible with these playtest rules.
Designed with a somewhat different ethos =\= incompatible. The new feats don’t have +1’s on level 1 feats, and the new races require level 1 feats specifically. That’s it.
Adamantine Armor - Does nothing now.
Like I suggested upthread, crits are either gonna have more context or a new general rule that makes stuff that effects monster crits work still, or the new crit rules won’t stick.
Why not just playtest in the spirit of the playtest and provide feedback about what you think of the crit rules?
Spore Druid Fungal Body class feature (14th lev) - Most important part of it now does nothing, and there is no easy house rule to address that. And as it's from a supplement, and we have no indication they will be updating every subclass in every supplement, it may just end up staying that way.
Except for the explicit statements that every 5e supplement with be compatible with the new core books.
Grave Cleric Sentinel at Death’s Door class feature (6th level) - does nothing now, there is no easy house rule to address that, and as it's a supplement may never seen an update.
The idea that Xanathar’s won’t get an update pass if any issues make it through the playtest to print is laughable. Theros? Maybe. Essentially no one cares if a given supernatural gift has a rules issue if used with a later product. But Xanathar’s and Tasha’s are going to be fully compatible.
The grapple issue impacts raging barbarians, rune knights using giants might, heck even the plasmoid from Spelljammer release literally the same week as these playtest rules has an ability that is no longer compatible with these rules.
The idea that the final wording of the new grapple rules won’t solve the “ability checks to grapple” issue is…laughable.
We have a TON of issues with short rests being phased to be only for hit dice recovery and not for restoring certain powers on a short rest.
This isn’t an incompatibility with anything they’ve shown us so far, and the fact short rests still exist tells us that they…aren’t looking to get rid of them. Hypotheticals aren’t incompatibilities.
All those things in books outside the core 3, we have no reason to believe they're all going to get updated. So they're directly in contradiction to the new core philosophy of not encouraging short rests for regeneration of powers.
That isn’t a rule.
What your trying to prop up as incompatible is…already extant in 5e.
Clockwork sorcerer chooses from certain spell lists which may no longer exist once they shift to arcane, divine and primal spell lists.
They have explicitly said that the classes and subclasses with have their own ways of accessing spell lists. The only reason to read that as “class spell lists won’t exist anymore at all” is that one has assumed the conclusion that it will be incompatible.
And this is just the first playtest package of 11-17 more monthly packages. My greatest concern is for all those supplements that are not the core 3. We know they will replace the core 3, but will they offer an update or errata for all the other books or just leave them behind like they did for 3e when 3.5e came out? I think it's reasonable to assume the later.
I think it’s patently absurd to assume the latter.
It requires ignoring the last decade, and the very significant shift in focus and design ethos between 5e and all previous wotc editions, at the publishing level. It’s even more nonsensical than the doomsaying in the VTT thread.
