This poem by Al-Būṣīrī is quite a famous one and most of you may have heard it on social media, the issue with this poem is that we do find major ghuluw (exaggerated praise) and shirk within it and this will be shown below.
For example when he mentions the fabricated belief that if it was not for the Prophet ﷺ the universe would not have existed:

Translation:
And how could the need of the one who
if not for him, the universe would not have been brought from nothingness, call him to the world
Qasīdat al-Burda Pg 253
Another example of ghuluw we see in this poem is when Al-Būṣīrī says the Prophet ﷺ’s name alone, would be able to bring the dead back to life when called over graves.

Translation:
If his miracles matched his rank in greatness
his very name would bring the dead to life when called over remains
Qasīdat al-Burda Pg 255
Also when he says every miracle, every prophet did was connected to the Prophet this ties into his light.

Translation:
Every miracle that noble messengers brought
was only connected to his light in some way.
Qasīdat al-Burda Pg 256
Now we find a case of shirk within the poem, Here Al-Būṣīrī says he swears by the moon, and we know from the hadith of the Prophet ﷺ that swearing upon other than Allah is shirk. Sa’id ibn Ubaydah said: Ibn Umar heard a man swearing: No, I swear by the Ka’bah. Ibn Umar said to him: I heard the Messenger of Allah (ﷺ) say: He who swears by anyone but Allah is polytheist. (Sunan Abi Dawud 3251, Ibn Abi al-‘Izz said, “If one’s swearing by other than Allah is intended to adjure Allah, that is also forbidden, as stating an oath by a created being for a created being is not permissible, so how can it be for the Creator?” (Sharh Aqeedah Tahawiyyah 1/297)

Translation:
I swear by the moon that was split, it surely
has a connection to his heart, and the oath is true
Qasīdat al-Burda Pg 260
Another case of shirk we find in this poem is him seeking refuge in The Prophet ﷺ. Not only that he says there is no one to seek refuge in except The Prophet ﷺ when calamaties occur, even the mushrikeen sought refuge only in Allah during calamities, yet Al-Būṣīrī says he seeks refuge in the Prophet instead of Allah during calamties.
Surah Yunus: 22 – He is the One Who enables you to travel through land and sea. And it so happens that you are on ships, sailing with a favourable wind, to the passengers’ delight. Suddenly, the ships are overcome by a gale wind and those on board are overwhelmed by waves from every side, and they assume they are doomed. They cry out to Allah ˹alone˺ in sincere devotion, “If You save us from this, we will certainly be grateful.”
Ibn Taymiyyah says: So whoever makes the angels and prophets intermediaries, calling upon them, placing reliance upon them, and asking them to bring about benefits and repel harms, such as asking them to forgive sins, guide hearts, relieve distress, or fulfil needs, then he is a disbeliever by the consensus of the Muslims. (Majmu Fatawa 1/124)




Translation:
Page 260- Time never brought me harm, and when I sought refuge in him,
I found protection from him that never failed.
Page 261- Nor did I ever seek richness of both worlds from his hand
except that I received generosity from the best giver.
Page 271- O most noble of creation, I have none to seek refuge in
besides you, when great calamities descend.
Qasīdat al-Burda Pg 260-261
