Edited: Please add this very necessary and simple access feature.

Is there a way to? There's no way I'm ever going to use GOG much currently because sifting through pages upon pages of DLC sucks. I just want to see base games, not DLC etc.

Not since GOG started adding feature tags to DLC, no.

Earlier, we'd filter for something all games have, like single-player (almost all have that, at least, probably the only exception so far being Gwent), but it seems GOG have started adding that tag to DLC as well.

That is a shame, to me that is the bare minimum of a search feature.
It makes searching through any sort of deal a nightrmare.

Consider this a post stating that I'm not a very enthusiastic customer on GOG then if I can't search easily and will stick to Steam who do searching better.
Hope to return to GOG and see they've added such a simple feature, I'm amazed they have such a clunky store because I've heard people talk about GOG like they're the messiah, but it feels pretty bare bones after a year of slightly using it and with Galaxy 2.0.