Grids are certainly useful in layout, but you should almost never use them when drawing footprints. Almost any situation where using a grid is useful (like the 0.5mm pitch row of pads situation you’ve used as an example) is something a computer can do. The ‘A’ in EDA is easily the most important part. Sure, sometimes you may need to tweak something, and grids are vital for that, but footprints, for the most part, are not something you should be doing at all. They’re almost always a pattern, and beyond that, you’re only allowed to ■■■■ up zero times when creating them.
Every footprint drawing has numerical dimensions, and creating the footprint involves typing them in and sometimes, for weird or special footprints, doing some manual tweaking (which often involves numbers that don’t snap to a grid at all).
The footprint wizard is great, but it is not super accessible right now. @Joan_Sparky has the right idea of doing it entirely by entering dimensional data, and is the most accurate and flexible method without a doubt. It’s also a massive pain in the ass 
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In my opinion, every footprint should be generated algorithmically if possible, and if not, then it should be generated algorithmically as much as possible, then tweaked manually.
Also, it’s, uh, about 100 times faster than clickery gridy tedium. First off, I am VERY aware I accidentally selected the wrong H/V pitch offset (I picked OUTSIDE instead of inside) but this gif is in real time, and shows exactly how much (or little) effort one should be spending making most footprints. Also, it removes a ton of human error, though, just as Jeff Goldbloom said about life, so too did my own idiocy ‘find a way’ to mess up the footprint. But at least it’s fixed with a quick change of a drop down menu :). Reddit thread with cross platform program I used: https://www.reddit.com/r/electronics/comments/3kmm06/gif_how_to_footprint/
I am certainly not saying this is the best program, but you should definitely be automating footprint creation to a similar degree through whatever means you prefer. You should not be manually adding most pads with clicks, save for special cases where manual tweaking is unavoidable. But even weird footprints like a PQFN 3.3x3.3 or some terrible TI package with pads that are shaped like a bunch of dicks and with 0.3mm pitch no less, you can usually automate the bulk of it.
Oh, and yes, I know I messed up the soldermask pullback too. Again, it’s a demonstration :).
