Yes, I’m advocating for using hours as a familiar unit

Like hogsheads per rod.

instead of kiloseconds or megaseconds or teraseconds. You’ll never get the world on metric time.

Those might be used eventually at some point in the future, but right now our life is dominated by the rotation of the earth, the movement of the earth around the sun, etc. So, other units that correspond to those natural events make sense.

But, I’m not advocating anything radical, just use the standard SI unit for energy instead of some awkward non-SI unit based on SI units where the only thing it has going for it is that it’s familiar.

If I’m doing calculations for solar panel production

You aren’t, I can tell because you advocate for kWh. And your denominator in that case wouldn’t be “per 3 days”.

We organize time around hours and days

And minutes, and seconds. Most of us use all of these.

so it only makes sense for there to be an hour-based unit for easy conversion.

No, it doesn’t. Joules are the unit that makes sense when talking about energy.