Text Size Styles [closed]

I'm looking at our company website's master style sheet, and noticed multiple styles regarding text sizes. Some of them are defined through H1, H2, Body, etc. Other are things like .content-hdr, .content-intro.

I thought we should stick to the standard set of styles like Google Material Design has, or iOS, which only define the H1, H2... H6, Body1, Body2, Footnote. These are native CSS styles. I thought we should refrain from using things like .content-hdr, etc - I thought these are custom styles.

But I haven't been doing web development for quite a while, and thought I should get advice from the pros.