This is so America-centric it baffles me, you sound delusional, especially that you think countries will convert to imperial. There is no country in the world thinking about that, and a lot of countries have converted from imperial to metric.
Your biggest complaints are that (1) metric units are not quantities you use in everyday life and (2) that you don't know how large a metric quantity is.
Both are just because you are unfamiliar with the system, people working with this system do not have this problem at all. Regarding (1), people don't care that a litre is too large too drink, they just know that a glass is 0.2-0.25L, so you can get 4-5 glasses out of a litre bottle. The benefit base 10 units is that they're easy to convert and use, people don't care if something is in cL/dL/L because it's just a comma placement away.
Regarding (2), people have a very good feeling about how big their everyday units are. E.g. a metre is about a step (large/small step depending on your size), that's fine for rough measurements, and about as (in)accurate as your "a foot is my forearm".
Your biggest complaints are that (1) metric units are not quantities you use in everyday life and (2) that you don't know how large a metric quantity is.
Both are just because you are unfamiliar with the system, people working with this system do not have this problem at all. Regarding (1), people don't care that a litre is too large too drink, they just know that a glass is 0.2-0.25L, so you can get 4-5 glasses out of a litre bottle. The benefit base 10 units is that they're easy to convert and use, people don't care if something is in cL/dL/L because it's just a comma placement away.
Regarding (2), people have a very good feeling about how big their everyday units are. E.g. a metre is about a step (large/small step depending on your size), that's fine for rough measurements, and about as (in)accurate as your "a foot is my forearm".