Firstly, we can divide a cup by 2, 3, and 4 in the kitchen because those are common measuring-cup sizes. Nobody is prevented from using a fractional size: if I divide a cup by 5 then I have 1/5th of a cup, nothing more and nothing less.
While 1/4th of a cup is 2 oz, and 1/3rd of a cup is 16 teaspoons, 1/5th of a cup doesn't divide evenly into a smaller unit and that's why "we don't do it", but there is nothing to stop the chef from using 9 teaspoons. [Or he can instinctively go up to 45mL on his graduated measuring cup, which almost always has both systems on it!] Teaspoons, tablespoons, ounces, cups, quarts and gallons are all inter-related multiples, and once you internalize it, you can convert like a boss.
While I'm sure it's lovely that metric measures divide by 2 and 5, that's all they divide by, so in terms of divisors, you've lost 3, 4, 6, 8...
So if it really is about dividing things usefully without resorting to fractions, then using a system that is nothing but multiples of 10 is a handicap, when we've had systems with lovely 12s and 16s with many different options for dividing them up.
But the metric people can simply chop up the measures even more finely and claim victory. For example, currency: it was in multiples of 16 or 8 which allowed for limited permutations. Decimalization chopped it into pennies, and we find 100 gradations in every pound sterling. All that did is make base-10 math easier for bean counters, and confuse people on the streets with a mystifying array of coinage. [Mental math indicates that it must increase the volume of coins per average transaction, as well.]
If a basic customary unit of length is an inch, many people can put two fingers together and estimate that on the human scale. But who can estimate or eyeball a millimeter?
Oh, and, have you ever found a nice British recipe in metric, shopped at your American grocery store, and prepared that in your American kitchen with your Fahrenheit range? You will eventually want to tip it all in the rubbish bin. Adam Ragusea suggests as much: https://youtu.be/TE8xg3d8dBg?si=SD8wLxD6ib6InLX4