If you make an illusion of a wall spell, and your party knows you do this, it will appear as a wall to the enemy, blocking sight of the party member, giving them advantage, but be transparent to the party as they already know it's an illusion.
Because of how it's written it's a highly abusable spell.
I wouldn't say highly abusable, but it could be abused once in a while. It's still a 5x5x5 cube max, so yeah good for a doorway, not so good out in the open.
As more spells get added Wizards will get better and better.
True dat.
Nothing says it can't. It says you can make sound that isn't static, so why would the image have to be static? Nothing says it can't be a moving or changing image.
Basically because:
a) higher level illusions explicitly have wording of "image of object or creature or other visible phenomena" instead of "image of an object"
b) it's called an image, not a moving image.
c) all of the examples are of stationary objects/images.
d) the authors went out of their way to make the sound non-static. That doesn't give the same property to the image.
e) if as you say, it is highly abusable, why would a DM want to allow it to be even more abusable?
I'm ok if someone runs it stronger at their table than the spell seems to indicate and yes, the cantrip does not explicitly call out a movement limitation, but I tend to go with RAI based on the writeup of Minor Illusion and the writeup of Silent Image (which is a first level spell where sound is taken away and the caster has to use an action to alter the appearance of the image to make it look like it is moving if the wizard moves the image). The writeup of Silent Image and Major Image indicate the ability to make the image seem real, so I don't give those properties to Minor Illusion which indicates that it is merely an image. Those writeups also explicitly discuss images of continuously mobile thing like a creature (or other visible phenomena).
To me, Silent Image allows for the illusion of a creek with water running in it (i.e. other visible phenomena), Minor Illusion does not (objects only). Minor Illusion is limited to objects that do not move, glow, spin, or do other things that the "visible phenomena / creature" clauses of the Silent Image and Major Image spells give to those spells.
I do think that the designers dropped the ball on this spell in this area.
But if Minor Illusion can do most of what Silent Image can do (and Minor Illusion also does not have a Verbal component), players would just spam Minor Illusion and only cast Silent Image once in a blue moon when they need a mobile illusion. That tends to make Minor Illusion abusable as you claim. I have this illusion of an archer firing arrows next to me in a combat. Sure, the foes lose track of the arrows, but since arrows move so fast, that can happen anyway. For the price of a cantrip, it gives the caster a fake buddy who might be attacked instead (and it doesn't need to be an archer, it could be a medusa or something worse). Hmmm. Pretty strong for a spammable cantrip.
So to me, an explicit reading of Minor Illusion does not have the "illusion of a creature or other visible phenomena" clause, so it does not get those properties.