It's not as simple of an equation as many might guess actually. It's not just about how many Guests are coming but about what Guests are coming. Right now, the "typical" Disney Guests (flying from out of state and staying for 6-nights/7 days) just aren't coming. Most of the Guests in the parks (especially now) are AP holders, locals, some drive-market Guests, and some DVC members. As a result, hotel occupancy at non-DVC resorts is just not up to where it needs to be, which is why you see hotels like YC and GF not opening select restaurants. There are brief periods of exception (like the week after Christmas) but WDW is not built to be a weekends and holidays destination. Even during those weekends and holidays, the parks aren't consistently selling out. One would expect -- at 35% capacity -- that every day in between Christmas and the New Year would've been sold out at all parks, but the reality was that maybe only two of those days were sold out across all the parks.
WDW just has too much infrastructure to be relatively empty most weekdays, so I'd argue that once they see more Guests staying in the resorts consistently (they aren't going to throw open the doors to tons of new shops and restaurants for one week only), you'll start to see more offerings. More resort Guests mean more Guests coming for out of town, which means longer stays (which, by definition, encompass weekdays).
So yes, capacity is a factor but first they need to be consistently meeting current capacity with Guests who are staying in their hotels. I think they'll be in a much better place in that regard by late spring or early summer. I'd also be stunned if they haven't raised capacity by the start of summer.