Tbh I disagree. The I believe is a great statement as long as you express why. It states your opinion, lets people know about you, and how you interpret your thoughts. Also makes it harder for people to disagree while sounding like an ass. In my experience, they're typically more respectful towards a belief even if they don't believe in the same thing. Very powerful and very underrated.
In an academic paper, one should never write "I believe/think." You can state your opinion, etc. without it. It makes you sound unsure of what you're saying. "I believe that the best solution is..." vs "The best solution is..."
The latter is more confident and the reader is more likely to accept it.
It varies on the professor. I was told by one to write that and had a whole class on the phrase. I regularly use it and excel with writing. It also depends on the topic. To each their own, but it has not hindered me as of yet.
Sidenote, believe and think each have a different tone. Think sounds more unsure or as if you are creating more of a hypothesis whereas believe is more personal and strong-willed.
The last one works great for my husband. He suffers from an Anxity disorder, and he found if he chews gum when he is in places that give him Anxiety it helps him immensely.
A man who cam smile even when he's so sad that he wants to die, when it's so painful that he wants to give it all up and run away, is a man who will become strong.
I say "I think" or "I believe" with things because 9/10 times I'm not EXTREMELY positive about what I'm typing or saying. Therefore I'd rather seem uncertain than a liar.
The latter is more confident and the reader is more likely to accept it.