I've tried my hand at making crab cakes.  Turned out OK but the remoulade sauce has been very mediocre IMO.

The recipes I tried were found online and consist of mayo, a dash of lemon juice, and spices more or less.  (paprika, cayan, hot sauce, etc.)

It turns out thick and tangy tasting.  Not creamy with a spicy bite like I've had even in restaurants that were far from top notch.  So what am I doing wrong here?

Restaurant ones probably have a little more oil in them.

Add horseradish to the mix. I've found that the wasabi paste you can get at the store is really quite perfect for this because it's been so finely blended that it mixes well and the chief ingredient is actually horseradish. If you use regular fresh grated horseradish you will want to mash the living fuck out of it in a mortar and pestle until it's essentially a paste. Horseradish is where the full spicy wonderfulness of remoulade comes from. All the other shit you put in it is just to tweak the HR & mayo flavor with more complex aromatics. If you're not adding a good pungent horseradish to it you're more or less making miracle whip. Also, don't use shit fucking yellow French's hot dog mustard. Use a proper imported mustard from France or England. They're on another level of intensity so use sparingly until you get your sea legs.

ETA: Some recipes I've seen include a tiny bit of anchovy. I would avoid that unless you really like anchovies and even if you do, start small and add because you can never deaden the flavor once it's gotten too intense.

Thank you guys.  A couple good tips I will give them a try!

Try adding scallion, garlic, parsley, green onion if you didn't. Your OP sounds like you only added dry spices. Make sure to chop it very fine. As above, add horseradish and some decent dijon.

I like to use a little Chipotle Tabasco. I won't use any of the other Tabasco. IMO the Chipotle is the only one that doesn't have an excessive vinegar flavor. Adjust to your liking.

Kew pie mayo mixed with a generous squeeze of sriracha and a generous squeeze of sweet chili sauce.