Hmm, I don't really see how the trade mechanic in game either follows nor contradict the 5e d&d rules so starting with "I know there are a ton of folks who want this game to be true to D&D rules" and later follow up with "So, why make the process so painful??? Just so we can say "the D&D handbook says" is beyond me, as per my knowledge, no one here on these forums has stated trading should stay close to the rules. In fact, most agree with you that inventory management and trading needs an overhoul.
As per the hide mechanic. Do you play as a rogue or ranger? Otherwise your skills in stealth would normally in d&d be so low with the other classes available right now that hiding would practically be useless and the current state of the of combat encounters and the action economy is something you can blame Larian for. Not the rule book. Also, you want even less to do manually in turnbased combat?