To answer the OP’s quetion
no.
“Is a Jewish magazine without a rabbi like a restaurant without a Mashgiach”
Yes both arent automatically assur. Both depend on the content produced. Now with restaurant you may not know what ingredients are being used so you may want a mashgiach to look out for you. But with a magazine you do know.
“we don’t need rabbis to tell us what kosher reading is?”
A mashgiach n a restaurant doesnt tell you what kosher eating is. the shulchan aruch does. All the mashgiach tells you i if the food produced follows the rules laid out. If you have anoher way of ascertaining it, say the restaurant is owned by person you trust, or the ingredient are all innocuous like bread from a goyish bakery centuries ago, or some products (beer, bourbon ) today then you dont need a mashgiach.
If you are not sure “what kosher reading is” then by all means bring a magazine to a mashgiach and have him inspect it.
Jersey, Joseph
“So sorry but you are incorrect. Hamodea has Rabbinic advisory and it seems yated has as well.”
Ami does as well. ITs masthead lists Rabbi Moshe Taub as its Rabbinic advisor.