What is the concern about Muslims calling others (e.g.: Anbiya and Auliya) other than Allah for certain things?

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

Dear brother,

Seeking help from anyone (Prophet, angel, pious person, Wali) other than Allah is major Shirk (polytheism).

Allah Says (what means):

• {And whoever invokes besides Allah another deity for which he has no proof - then his account is only with his Lord. Indeed, the disbelievers will not succeed.} [Quran 23:117]

• {And do not invoke besides Allah that which neither benefits you nor harms you, for if you did, then indeed you would be of the wrongdoers.'} [Quran 10:106]

The Prophet said: “When you ask (for something), you should ask it from Allah, and when you seek help, you should seek it from Allah Alone” [At-Tirmithi, Ahmad and Al-Bayhaqi]

The Prophet also said: “I shall not be called for help. Indeed, it is Allah, The Almighty, The Great, Who should be called for help.” [At-Tabaraani]

Allah knows best.