Easi-fill to level before tiling?

I'm ready to start tiling my shower enclosure, the area has been tanked with a paint on membrane, but the wall is noticeably uneven, with significant bulges and dips, up to around an inch out in places.

I don't mind if the tiles don't look perfect, but I at least want to do an acceptable job, so I was wondering if I will need to level the wall before tiling rather than just applying varying thicknesses of tile adhesive as I go to try to level out the worst bits?

Would easi-fill on top of the tanking membrane and behind the tiles be stable enough, or might that lead to problems down the line?

Any thoughts appreciated.

anything that needs an inch of building up really needs re-boarding. re-fit it with a backerboard instead

Thanks for the reply, not an option due to several constraints unfortunately, so really it's between tiling straight onto the uneven wall and accepting the fact that it's not going to look great, or filling in the low points before tiling onto it. Looks like I'll just have to go ahead with it and hope the tiles don't all fall off a few months down the line!