You wrote: "I heard that Miricle Grow eventually kills plants..."

Not so. That's an extreme view. And it's a poor argument if one wants to encourage people to use "natural materials."

Miracle Gro works fine when one follows the directions.

Beyond that, all things are toxic when used in excessive amounts.

Fertilizers are, by their nature, salty, since they are made of salts. Probably the best way to avoid overall saltiness is to use a very high analysis material (e.g., 20-20-20 vs. 8-8-8), and use less of it. Then, at least, you are getting less non-nutrient salt.

There are some that are lower in chloride, generally much more expensive. You could look for materials that use salts other than the chlorides, and for which both the cation and anion are nutrients (e.g., potassium sulfate, potassium nitrate, ammonium nitrate, mono- or di-ammonium phosphate, etc.), and that may give a lower total soluable salts level.

Why do you want to do this? Is your soil inherently salty? In areas of Florida with salty soil and salty irrigation water, the solution is generally to go to very high analysis materials and to use them in small quantities, more frequently, then hope for enough rain between applications to move the salt lower into the soil profile.

Using epsom salt around citrus trees. If brodcasting and not mixing with water, how much to brodcast and how often?