I raise cattle (one day for a living, but now a side job and for my enjoyment). Your read on the feed is very true for the feedlots, not trying to discredit that, because if you buy your beef from a feedlot than this is very much the case -- chances are if you don't know where you beef came from, then it came from a feed lot. If your packing says "Grass Fed" than it just means they spent most of their lives in a pasture before being shipped to a feedlot for a miserable last three months of life, so chances are you probably don't know where your cattle came from, even if you're going on the packaging in a grocery store, and it's actually grained to some extent.
There are a few exceptions to this, even in stores. If you buy from Whole Food and get their brand beef, it's grass-only. I know the largest rancher selling to WF, we're friends -- my teeball team beat his teeball team in the season finals last summer.
I mostly raise dairy cows, but if you're going to go through the effort to raise one sort of breed of cattle, it's trivial to add in an even lower maintenance cattle as well. As a result I have three or four animals in my pasture right now who are getting ready for freezer camp. My neighbors are all beef ranchers, I am the exception. But none of us are feeding grain to our cattle. My area sells a massive amount of grass-only beef. We have the luxury of this being basically free for us to do and then having found a niche market willing to accept a lot more money for their beef if it was raised right and fed right. I don't sell my beef the way most folks do, so unless you know me personally, you've never eaten my animals or had our farm's dairy products.
All that to say, there are very good alternatives to feedlots. My beef cattle only need supplemental food (aka more than the green grass in my pastures) between December and April. I did the math, it costs me $140 / year to feed out cattle and it takes two or three years for an Angus to be butcher-weight. That's $420 on the high end for a grass-only steer that'll dress to like 600lbs of beef.
I'd get by with even fewer days feeding except I also own and breed Appaloosas and horses are much harder on the pastures than cattle. If I ran two herds my cattle would keep the pastures in grass until about January -- and with this warm weather I know folks who have YET to feed hay! But with my horses mixed into the herd it means that the grass is killed if I keep them on it -- horses have top and bottom teeth, they can cut grass clear to the dirt but cattle only have bottom teeth and they'll leave about 1/2" of grass on each blade, meaning the grass can continue to regenerate all winter if it's wet and warm enough.