Frustrated with elders on feeding LO solids

Why all the elders have all sorts of funny ideas when comes to feeding LO solids? My parents and MIL kept telling me to add salt or soy sauce into his food, and kept saying the reason that he don’t like to eat food is because there’s no seasoning. Feeding LO is already very stressful, and have to deal with all of their salt and soy sauce nonsense is even more frustrating!!