HVDC is the grid's distant future if the future is mostly solar. Why bother inverting to AC if everything making the power is fundamentally changing over to DC?
Easy: because DC voltage conversion is way harder.
You can't really build a "grid" out of HVDC, because you can't easily convert between what the solar plants produce (a few hundred volts), what the local distribution grid needs (a few thousand volts), and what is needed to get that power across the country (tens of thousands of volts). On the other side you need to convert back down to a city-level distribution grid, down to a street-level distribution grid, and in your home down to whatever your equipment needs.
DC-DC conversion is significantly more expensive, more failure-prone and less efficient than AC-AC conversion. Why bother with a bunch of expensive active electronics when a simple transformer can do the job even better? Besides, who's going to pay to retool the entire country? Just because a solar panel produces DC and your computer needs DC doesn't mean it's viable to use DC for the entire chain.
HVDC is excellent for long-distance transmission lines, especially when power almost always flows in a single direction. Want to hook up a solar plant in the desert to an urban area 1000km away? Use HVDC! Replacing the entire grid grid with it? Probably not the best idea.
This. AC generation is also way easier to reliably engineer at high power than DC.
Remember, early generators from Edison’s company were DC. They caught fire _constantly_. Obviously technology has caught up since then but AC power generation and distribution is simpler engineering overall. Use HVDC where you need it and it is cost effective to do so.
