Block entities (those with complex data, like inventories) can be read/interacted with by redstone (a regular-ish set of blocks in terms of data), which can then trigger a piston or dispenser (which changes the world), and said piston or dispenser can then interact with the players movement, pushing them, or hitting them with an arrow, or dispensing water that changes their movement.

Same again for non player entities, but also factor in their AI having to adjust pathing based on the world changing.

It really can't, though. Parallelization is the enemy of consistent game mechanics, especially in a complex sandbox game like minecraft. There are tons of things that interact with each other in minecraft's world - if you just tick everything at arbitrary times, those interactions cease to be deterministic and might break entirely unless you write a ton of spaghetti code to deal with every edge case. Redstone in particular is the best example of a mechanic that heavily relies on the synchronous nature of the game logic loop.