Taking one of the implementations of the great wall, here's Katago's evaluation, rounded to half a point:
Overall, Black loses 15,5 points by playing this opening.
Katago "sees" this application of the great wall. and continue splitting White's positions, while already projecting something of a side & center framework. Black invades and White's safest route is to answer conservatively with the turn at . Cutting and at a is possible but will lead to an all board fighting game for which this opening is intended.
Katago recommends to be more severely played at a. If White continues playing cautiously like this, the advantage shrinks back to 13 points.
At the bottom, White can afford to kick with because of the marked stone played earlier. Black continues his aggressive pace with . The continuation is interesting: White can continue his peaceful game at a or reinforce at ''b' but in both cases Black will launch an attack on the other corner.
loses a point according to Katago. The ladder works for Black, so that White will have to spend moves to capture the cutting stones and . Black can wrap around White on the outside. Still no real issues but fighting couldn't be avoided.
KataGo prefers to deal with the previous variation. Black then invades at . The idea is of course to live in the corner and push White's outward group towards the great wall. is annoying but White can actually manage this quite well. Again, fighting is hard to avoid.
Uberdude: The 2-3 invasions of is an interesting and rarely seen move. I suppose the more normal idea of 3-3 invading and going for a ko makes it too easy on white? The great wall seems useful in making white's 3-3 reply for fail to a ladder: