Unfinished wood furniture is great for a bunch of reasons. It's often more affordable that pre-finished furniture. Plus, it's real wood, unlike other cheaper options made from laminate instead. And lastly, you can customize it to work with your existing decor.
If you're in the market, here are the best places to find what you're looking for:
Urban Green is a Brooklyn-based company making furniture that’s both sustainable and stylish. They have a basic Parsons table and other low-profile styles that bend more modern. They aren’t the cheapest option but the updated looks might be worth it to you.
Table Legs sells…wait for it…a lot of wood table legs in a range of styles. But! They also sell unfinished tabletops. You have menu of options and can specify shape, size, type of wood, edging, and corners. Their table cleats also look like they’d be handy...
International Concepts is a line of unfinished wood furniture found at various major retailers like Amazon, Wayfair, and Home Depot. It is mostly traditional, but also includes some simple basics that can be easily adapted.
Etsy has a smaller selection, but there's still some good stuff — most notably these great floating wooden shelves from Wood Creations 4U. Since you are dealing with independent makers, many sellers will also customize pieces for you, or you can commission something special.
Check around your local area as well — there are sure to be independent retailers nearby where you won't have to pay for shipping.