The first issue is too much or too little description. The second issue is how the plan for the writer to be the director explains or excuses the amount of description (among other things).
The description that clearly feels excessive to me generally is based on these impulses:
1) Location geometry
It rarely actually matters -- in a script -- whether the dresser is to the left or the right of the bed. Yet many writers get a vision in their head and are compelled to record a lot of details about such things.
In practice, of course, should the film be produced, the actual room may be quite different but the scenes are likely to be fine. So, the question of where everything is should only be detailed when dramatic action critically relies on it. Even then, many things can be described very simply.
2) Blocking the actors
It’s just not necessary to say that someone opens the car door and gets in. Or that they walk around the car to get in. Unless these details are critical to action, they are unnecessary. “Gets in” is all any reader needs to understand that someone unlocked the car door, opened it, got in, adjusted the mirrors, started the engine, put the car in gear and moved away. If there is a dramatic reason to describe everything (the character suffers from OCD?) then, of course, fine. But otherwise, less is more.
3) Directing the actors
Actors are creative. Describing in detail when they brush the hair out of their face and after which word they pause should be unnecessary and may be considered intrusive. The script must make it very clear what the character is feeling. The character may even have a set of typical behaviors. Fine. Just don't get hung up on a lot of detailed description of ordinary movements and reactions. Save this for when a character does something completely unexpected.
Apart from those common problems, I see the pros and cons of action description this way:
|Too Much?||Too Little?|
|PROs:||Might clarify the writer's intention better||Brevity is a good thing|
|CONs:||Current style: keep descriptions brief, e.g. 3-lines||The feeling is opaque or invisible|
|Florid or excessive description is often bad writing|
|A long impassioned description may actually lose some readers|
"It’s OK, I'm going to direct it myself"
Many struggle with the fact that a script is not an end product; it's the beginning of a process. A process that will be completed by a director who, in turn, drives the production.
Nevertheless, I would say that erring on the side of too much description is likely to be better. I've read scripts where it was impossible to tell what really mattered in a scene and the writer-director simply asserted that they planned to work with actors to bring that out. I'm thinking actors need the script to give them a clue beforehand, perhaps even before they decide to participate.
My own script, that I am going to direct, should be no different than the best possible script I would write to sell or have someone else direct.
Why should I go through all that “bother?” For the same reason I write in my journey or discuss a plan with colleagues: to understand myself better. Having the discipline to both commit to and to fully express what you (the writer) need in the story is a huge benefit to you the director, producer and cheer-leader.