I think they were saying that a investor-backed company only has a pathway to either (a) acquisition, likely by a public company, or (b) going public. Investors need (a) or (b) to get a payout, that's their business model, that's the reason they invest in your company.

If you avoid the venture investor route, you can avoid both outcomes (a) and (b), keep the company privately owned, just stay awesome and customer-friendly forever, and avoid being forced to eventually prioritize shareholders over customers.