[throwaway154]

    body {
        font-family: sans-serif;
        font-size:  16pt;
        line-height:  1.6;
    }

    h1, h2, h3, h4, h5, h6 {
        font-family:  serif;
    }

That's readable, thus a minimum standard for beauty.

Use of colour, spacing, case, image then become important for making powerful prioritisation, focus, structuring absorption/presentation of your message. A specific font may or may not be part of this, and advantage of system fonts is not just their speed, but their familiarity - this can also be a disadvantage if intentionally seeking to disjoint a user or place them in a context associated with the font.