We're from Crystal Delta solutions, partners of Canvas instructure. We do have Loree LTI in Canvas which will make designer life easier to design a page without HTML/CSS knowledge.
We used to load the google fonts and custom fonts via CSS/JS in the Canvas themes, our clients are facing the load time for fonts and meanwhile the fonts are default font styles like Times New Roman or Lato.
We investigated how this load time is caused and came to know that the Canvas CSS/Js is loading first and then the Custom CSS/JS is loading. We raised a partner request for this issue (Case #08280319  [ ref:_00DA0Ibsk._5003m1FMBcN:ref ])
We got the reply to raise the suggestion for future implementation.
It would be great to load the custom CSS/JS parallelly or first to reduce the load time.