I have a Tidy Vap and I love it. I have severe asthma, and now I can actually get my floors and counters and shower and bird cages really clean, because it cleans without using detergents that made me wheeze. It does sound like yours may be defective, because even my $60 Scunci did a good job at cleaning - it was just very inconvenient. Sue

There are two things you want: 1) you want the light bulb enclosure to be gasketed. Normally the gasket is between the trim and the can, and it's all held together with crews for a tight seal. That will prevent vapor from entering the fixture. Gaskets that are held together by the trim ring just springing up on the housing? Not good enough in my opinion. Meaning, if you ever need to change the bulb you should need a screwdriver. 2) You want the fixture itself to be sealed to the ceiling, meaning there should be no way for vapor to get between the ceiling and the light housing. You don't want vapor getting into the framing bays of your house. With Kerdi, I'll seal the Kerdi to the light's housing with Kerdi Fix. Will a "wet rated light" suffice? Maybe, maybe not. Depends on its design (see #1 above) and with the installation (see #2 above) details. A vapor rated light meets #1, but it still need to be installed correctly. Last two steams I've done, one used "Nicole II" lights, the other used one called "Cora". Not all vapor-rated lights are expensive, but those two were. Wet and vapor-rated assemblies? It's a somewhat code-ambiguous issue where I live. But what I wrote is my way, and I tend to lean towards bullet-proof construction. Mongo

Your options are limited to vapor proof lighting. Not just wet rated. Vapor sealed is the requirement. Here is one option. https://ledlightsworld.com/products/waterproof-ip65-non-dimmable-cri-80-round-shape-recessed-led-downlight-fixture-vapor-proof-fit-for-shower-suana-and-outdoor-lighting

That is a warrantyless frankensystem. Big red flag. Schluter DS is the only membrane with a low enough perm rating for a steamer. Not standard Kerdi. Sounds like a seat of his pants, not really knowledgeable installer.