The concept is misleading really. The term "hit points" implies a "hit", as in physical contact. Sometimes that might be case, other times it isn't. That is the abstract part IMO. This is one of the reasons why I describe HP as "combat effectiveness." When that is "attacked", the effort to resist a successful attack results in a loss of HP. Is that physical damage? Maybe. Is it effort to avoid the blow? Maybe.
Even a critical "hit" doesn't necessarily mean a hit. It means a very effective attack was conducted and results in more effort, luck, skill, or whatever to avoid, turn into a lesser hit, or whatever. Off hand, I don't know of anything that is immune to crits in 5E, but I could be missing it.
I agree for things such as poison, HP is not a great model given its abstract nature. For such times, you have to assume actual contact was made, but even the damage from the hit and the poison itself can still be reflected in the loss of HP as a measure of skill, toughness, luck, etc.
Finally, the AC granted by armor already reflects the DR it grants. For example, if a "hit" or effective attack fails against an AC 20 (due to plate and shield), but succeeds against an AC 16 (maybe studded leather and high DEX?); is it reasonable to assume the attack physically struck the lower AC (despite high DEX to avoid being hit) and physically missed the high AC? No. That is nonsensical. The stronger armor would have absorbed the hit and negated it (which is what DR is after all). The measure of protection provided by heavier armors is inherent in reducing damage by the fact they have a higher AC. DR is not required and is "double-dipping" if used as well. All that being said, it assumes the attack resulted in actual physical "hits" and such and not metaphysical/abstract damage, etc., which we know is not ncessarily the case.
So, if you want a more complex system that is fine of course, but if you think attacks in D&D require actual "hits" and "damage" you are not interpreting attack or HP the way they were intended IMO. Either way, I agree losing the Touch AC mechanic was not a good idea. There are definitely issues in 5E, such as the fact you have to make an attack roll with a net. Reasonably, hitting someone in heavier armor would be easier than someone in no armor; yet the heavy armor has the higher AC and is harder to "hit" with a net. Things such as that don't make any sense IMO, which is why we changed the mechanic for nets to a DEX save and not an attack roll.