The problem is we have turned something which is harmless in moderation into a massive food business build on a model of addiction.
The thing that will make you unhealthy is highly processed food devoid of nutrition that is made entirely of starch, vegetable oil, sugar, salt and MSG that has replaced a healthy diet.
If you eat fresh fruit, vegetables and a moderate amount of meat, cooked healthfully and sprinkle a bit of seasoning on it for flavour you will likely be no worse off than consuming the healthy stuff without seasoning. Though if you use good ingredients you probably don't need the extra refined product. There are plenty of natural ingredients rich in glutamate.