Should everybody be eating oatmeal?
Unless you're allergic to oats, there's no reason for you not to eat oatmeal. If you have celiac disease or a gluten allergy, you'll want to check the label; oats themselves are naturally gluten-free, but many are processed in the same facilities wheat is, so unless a brand is certified gluten-free, there may be some stray gluten floating around.
Since oatmeal can admittedly be a bit bland if you eat it plain, Ansel recommends adding ingredients like cinnamon, cardamom, sliced almonds, chopped pistachios, tart dried cherries, or fresh berries. "Also don’t be afraid to go savory by making an oatmeal 'risotto' by cooking it in chicken stock and adding sautéed shallots and spinach. Then top it with a fried egg for extra protein."
If that sounds like a bit too much work, you're in luck: slow cooker oatmeal is a totally legit option that doesn't require you standing half-asleep over a stove. If you're too lazy for that, there's always the overnight oats route -- it's like regular oatmeal, but cold.
Is it possible to eat too much oatmeal?
As beneficial as beta-glucan is, eating oatmeal for breakfast, lunch, and dinner means you're gonna be neglecting other parts of the (admittedly flawed) food pyramid. According to Ansel, this can translate "to all kinds of nutrient deficiencies over time, not to mention diet boredom."
Then again, the odds of you eating only oatmeal 24/7 are pretty remote -- unless you're a quaker, or that dude Bob with the red mill, in which case your body's probably 90% oats anyway.