It isn’t exactly humanism, but it is humanism with a Christian overlay (or perhaps vice-versa). Either way, it denies the sovereignty of God and gives the power of salvation to man but does so in language that does not explicitly say that, but the implication is always there.
I was United Methodist for years. I taught and preached from the Wesleyan perspective and I denounced Calvinism every chance I got.
Then one day, the pieces fell into place and I knew that Wesleyan (or Arminian) theology is flawed. I spent a year studying to find why I was wrong. When I asked, I would hear circular arguments and would find educated scholars just saying “well, you just got a believe”.
I believe, but not in Wesley. He was a great organizer and SJW and that’s why he is famous today. But as a theologian, he should have listened to Whitefield.