It’s enough. We also don’t have any illustrations on our website. Just text that explains our value proposition.
How many logos do you know? Apple, Google, Uber. Logos a damn hard.
How many companies do I know which I do not remember a logo? Stripe, Segment, etc. billion dollars companies which I know without a logo even though I might use them every day.
So, to just sum it up. You don’t need a logo, or design guidelines until you’re big enough that you can easily spend $10-50k to shape your brand — because that’s how much it usually cost for a good branding. Everything else will most likely be a waste of money, and more importantly waste of your time.