Let's look at it from a scientific point of view. It all depends on how the table is set up. If you are playing on a box with huge pockets and wide pocket angles, then yes, skills will never improve.
Now, play on a 7 foot table with 4 1/4 inch pockets and a 141 deg pocket angle and deeper shelves. Very different animal. Research Penguin Pro Cut Rails.
Our 9 foot Gold Crown has standard 5 inch pockets. I think it plays easier then my United bar box with 4 3/8 ( I re measured... they are slightly less then 4 1/4)pockets. I dont rattle pockets on the 9 ft like I do on the 7 foot.
Let's use an analogy that some of you rifle shooters will appreciate. Rifle accuracy is usually described in MOA (MINUTE OF ANGLE). If a rifle will hold 1 minute of angle at 100 yards, then it will be the same 1 moa at 50 yards. In a no wind condition and a solid rest, it is exactly the same to shoot 1 moa groups at 50 yards, and 1 moa groups at 100 yards. It is just as easy to shoot 1/2 in groups at 50 yards as it is 1 in groups at 100 yards.
Same with the tables. Bigger pockets on the bigger table will play the same as a smaller table with smaller pockets. Of course that doesnt take into account the tighter traffic on the small table.
To conclude, if you are playing with good cue ball control, you wont have any longer shots on a 9 foot then you would a 7 foot. Now, if I reduce the 9 foot pockets to 4 1/4 , then it's a whole new ball game.