Significant elements of the game (like exploration) changed beyond recognition between the final playtest and publication. Another example is the sorry fate of the original playtest sorcerer, and its replacement by a tepid simulacrum that seemingly no-one wanted, for reasons we don't understand. Everything I've heard from playtesters suggests that WotC were more interested in making a game that 'felt like D&D' than a game that was actually good.
As for arbitrariness: no, good design is intentional. Every part of a game should be that way for a reason. In the case of 5e, the reason for many, many design choices seems to be 'it's tradition'. The entire druid class, for example, is basically a fetish. Why isn't the druid a type of cleric? Why don't they wear metal armour? Why do they use sickles? Why is the druid the shapeshifter, instead of a dedicated shapeshifter class? Because the druid is a grab-bag of self-referential D&Disms, all of which are important to the game's brand. The ranger has the same issue, only worse, because a large chunk of ranger players actively hate that it has magic (an arbitrary component that doesn't fit the fantasy), but rangers must have magic, because its tradition. That's before we get into the nuts and bolts stuff, which isn't any better.