I don't own a 7-seat MY (I have checked it out in-person at a local SC), but I have owned a 2008 Toyota Sienna for many years now and I can give you one point-of-view. We usually only use the 2 rows in our minivan with the back-row down so we can have a crate for our dog and plenty of space for other stuff. If you envision 95% of your usage as a 5-seater, then the Model Y could be a great option as a family car. But it isn't really a minivan replacement in my mind for the following reasons:
1. Sliding doors. These are so nice to have especially when young kids are involved. You don't have to worry about clearance with cars parked next to you or your kids opening doors into other cars. Entry and exit is really easy an convenient. Reaching across to help kids buckle/unbuckle or grab things out is really easy.
2. Headroom and general spaciousness - The MY needs to be a lot more aerodynamic and while legroom is quite good for the 2nd row (not great at all for the 3rd row), you are going to generally be way more comfortable in a minivan on long trips. I've driven with 5 adults and 2 kids (2 adults in the 3rd row of the Minivan) on very long trips with no one getting too cramped or uncomfortable. For the MY 3rd row, I would hesitate to put adults back there because it feels really cramped. I'd view it as either a spot for young kids, or generally a row to use in a pinch for shorter trips where you need the extra seating capacity
3. Storage - I think the MY has a lot of storage, but you can cram a lot more stuff into a minivan when you are going camping, etc, if you also need the 3rd row up. I think the 5 seater configuration does provide a lot of storage, especially when factoring in the frunk and potentially using a roof-rack.
In general, I think the MY is a great option if you don't need the 3rd row at all times and only want it for some added flexibility in a few situations when you need it. If you need the 3rd row most of the time, a minivan would be a much more comfortable option imo. For me personally, because we usually only ever use the 2 rows, with the dog in the back, the 5-seater MY is looking like a great fit for 90% of our needs and I will be trading in my old sedan for one within the next year or so. We'll still hold onto our minivan for a while longer. I am still curious to see what other 7-seater owners have to say about their experiences.