The finished job is shocking IMO. I presume that the "new" wall was built by the builder and therefore he should have made sure that it was suitable to tile before commencing.
If the tiles were not flat, this should have been demonstrated and alternative options (i.e. change tiles or layout) should have been discussed prior to work commencing.
I suggest that you discuss with your architect the "quality" of the work and get the architect to raise the issue with the builder if you are not comfortable of bringing to their attention collectively. Whilst you are discussing the tiling with your architect, can you ask why plywood has been used in a wet area and what tanking (waterproofing) has been applied prior to tiling, please? The walls should have been built using, preferably, cement boards or cement lined poly-core boards which don't require tanking, or at least plasterboards that were subsequently tanked prior to tiling.
Unfortunately, this is not going to be a quick fix as the walls are constructed incorrectly and the wall tiling is a secondary inconvenience, IMO.
Good luck,
Daz