The grouting looks sloppy, especially on your accent tiles. Caulking should be used in the corners.

The tile you picked out looks nice together.

What level of professional did you pay for? Just of the boat, starting out, side job, journeyman or artisan. The answer to your dilemma could be in your choice of professional.

Lippage on the large format tiles and blotchy grout is a concern. The accent appears to be Lunada Bay which is cast glass and will have creases & uneven edges. Contrasting grout will exaggerate this characteristic of the glass. Grout should still be smooth.
The accent should be slightly proud of the large format. Flush would be acceptable but NEVER recessed and trowel marks should not be seen through the glass.

Agree w MS and CTEC. hardway to learn

Awful , have no idea what their qualifications were but they lied. The corners are bad and the lippage unacceptable but happens with tile choice sometimes.

Looks like a very ambitious DIY

If you paid the typical 7-9K for a properly built and waterproofed shower from a craftsman, you got took. Looks more like the $1998 parking lot special.

amateur job......

I wouldn't be happy either .I think you should trust your instincts.

Even a first time DIYer would know enough to be ashamed of this work. The tiler knows, too. Evidently, he has no pride, no shame and no integrity if he grouted in this mess and tried to pass it off as acceptable work. I really hope I'm wrong and that he'll think better of it and refund your money.