WotC only failure here was not making it clear that isn't exactly an action economy in the same strict sense of the previous 2 editions.
The way a turn works in 5e is rather a simultaneity of everything you do. It starts with the fact that you can "split" your movement as you wish. That's because you mostly act with your arms and move with your legs after all. Similarly, many bonus actions are augmentations of the main action (e.g. smites and other spells intended to boost the subsequent attacks) or of the movement (the Rogue's Cunning Action). Have you noticed that the majority of bonus action spells have verbal components only? That means you are casting them literally by speaking, which is simultaneous with everything else. Even two-weapon fighting might be seen as smacking a foe with both weapons at once, although that's quite a bit of a stretch of the imagination.
The fact that the resolution of the actions is sequential is more for obvious practical reasons, and to give a player the chance of choosing them one at a time instead of declaring everything in advance, but from a character POV everything is hectic (and even simultaneous with everyone else's turn).
There are some details that frustrate me too: how Ready works with spells (i.e. it doesn't, forget about it) and the hard limit on the free interaction with one object (too hardcoded, I'd leave it up to the DM). But if you manage to get used to thinking of actions more simultaneously than a set of finite "slots" that fill your turn, I guarantee that it'll stop bothering you.
