Lot of the answer depends on what you mean by designer. It's generally a bad idea to hire a "specialist" on the early team unless it's THE core technical problem or User Interface problem you need to solve for. And then if you pivot, you'll need to let this person go.
What many people seem to be describing in "designer" is someone who understands the customer and guides the product to actually solve a real person's problems (usually framed as a customer segment or even better as a detailed customer profile with the pain point laid out). I've generally found this to be something that your product lead needs to internalize...so if your product lead has a "design" or other background, that can be really helpful (and may be a hiring requirement).
I've found that many pure-play "designers" don't actually understand user or human centered design (they tend to come out of graphic design or an aesthetic school) and that profile won't really help you other than add some window dressing that may get in the way of what your customers are looking to do and how you're A/B testing your product to see if that's actually happening.
It's not the label, but how the work gets done in the right way that you need to solve for.