The price isn't an issue with the practicality of the phone itself, although it is an issue with practicality in general. But that practicality depends on your means, as well as the practicality of combining the cost of a tablet and phone into one device which means that the Fold 2 can actually be cheaper than the aforementioned combination. From a practicality pov having your tablet and phone in one device can also be an advantage, no more syncing, no more hotspotting or paying for an extra LTE device, etc.
The thickness can certainly be an issue, I don't think it will be an issue for me personally as I understand the trade off. But even with that said I don't think the thickness will really make it impractical, but it definitely will be one of the top items on the wish list. Here it is next to the Duo, both unfolded. The hinge end is thicker though, especially with the air gap.
You can text and have phone conversations on a LTE smartwatch. But I get your point, it's still nice to have the full device.