I Could Use Some Clarification

I haven't had the time to sit down and read the complete MYMU information, so could someone explain in as much detail as possible why others are saying it's a nerf to mages? I'm open to any information at all.

If you think that it is a positive change for mages, please clarify that as well! I'm always interested in the community's oppinions

Using examples would be great as well as again, I haven't had time to sit down and read/process the complete notes

P.S.- I'm prepared for the downvotes due to my admittance to ignorance, tis the way of the boards