I am not sure is you agree or disagree with me here. I think having disadvantage on skills you don't have sound like a nice mechanic.
Give the Rogue two backgrounds, and every other class one.
Done.
Why do you find it so difficult to believe that the new feats will be powerful enough to be worth taking?
Well yeah, if it's a choice between +1 STR and something like Cleave, then it won't work.Because it's often more important to connect (hit) than to deal raw damage. That's only considering combat. Since ability checks are also used (supposedly) for many more things in 5th Edition, that makes them even more important.
Let's say I'm a fighter and I boost my STR. That boost to STR applies all of the time. If my alternative option is to have a bonus which applies only in certain situations, that alternative option is (IMO) not as good. I feel that way because I can look back across both 3rd and 4th Edition and see how that train of thought lead to so many feats in those editions being choices which were virtually never taken.
Any news on when the new playtest is expected?
Well yeah, if it's a choice between +1 STR and something like Cleave, then it won't work.
What if that's not the choice, though? What if it's a choice between having +1 STR and having three level 1 spells per day? What if it's a choice between having +1 STR and having an army of zombie minions? What if it's a choice between having +1 STR and being able to fly?