People are just used to kWh. There's nothing about it that's more intuitive, it's just more familiar. But measuring things in hogsheads and barleycorns used to be familiar too. Sometimes being familiar isn't as important as following standards. Eventually the standard units will become familiar, and since they're standard units, they're much easier to work with.

not actually understand how power usage of watts of appliances would convert into Joule energy units

1 joule per watt each second. It's dead easy. That's why Joules should be used.

That’s why electric cars motor powers are still rated in Watts

Yes, power should be measured in Watts, that's the standard unit for power, just like Joules are the standard unit for energy.

To add to that, that’s why so many metric countries (not USA) still use imperial units colloquially because they are more relatable in real life like

No they're not, it's just that people are used to them. The people whose minds are the hardest to change are the old people who have used some random unit for all their lives and don't want to have to get used to some newfangled standard (a standard that's actually hundreds of years old at this point). Because the old people refuse to change, the country gets stuck using that old unit, even if it's informally, and so that's what the kids learn, then they become old people and are also inflexible.

There's nothing about an inch or a pound that's naturally more intuitive than a centimetre or a kilogram. It's just what you're used to. Go somewhere where people grew up with metric and for them using anything other than metric feels strange and awkward. Pilots and sailors are used to knots, they never had to switch, but when they do complex calculations they mostly avoid using knots because doing conversions with non-SI units is such a massive pain in the ass.