hmm, I thought of a good analogy.
Imagine that the competitive landscape is a mountain. The best players are at the top, beginners have to work their way up from the bottom. People compete by throwing rocks at each other, so you can only win against people that are within rock-throwing distance, or if they are lower than you.
The depth of a game is how tall the mountain is. If a mountain is only 5 meters tall, then the distance seperating the top players and the bottom players are still within a stone's throw. Anyone can beat anyone. The game has little competitive depth. Whereas a mountain that's 10km tall, then there are nuances that seperate even players in the top 50% from the top 49%.
The accessibility of a game is how steep/shallow the mountain is. (theoretically you can have a very shallow mountain that is nevertheless very tall - it just means the mountain covers a huge horizontal area. but that's not relevant to this analogy
) As an example, BBCS1 Taokaka had an impassable cliff for me in the form of taunt loop - it was a requirement of her game, but even doing 1 taunt loop was impossible for me with the amount of practise I was willing to put in or my reflexes. There were no "baby version" taunt loops for Tao, there were no "still viable but easier non-tauntloop combos" for Tao. It was a cliff that made me give up that character.
If instead BBCS1 Tao had a gentle slope instead of a cliff (like the simpler alternatives I mentioned) then I might have made it further up the mountain and possibly even mastered the tauntloop gradually. But the giant cliff in the way made it unfun and I gave up.
But I digress. So yeah, depth = height, accessibility = slope