There’s no big advantage for those cases where an assertFoo exists that exactly matches your intent. In those cases they behave almost the same.
But when you come to checks that are somewhat more complex, then the advantage becomes more visible:
val foo = List.of("someValue");
assertTrue(foo.contains("someValue") && foo.contains("anotherValue"));
Expected: is <true>
but: was <false>
vs.
val foo = List.of("someValue");
assertThat(foo, containsInAnyOrder("someValue", "anotherValue"));
Expected: iterable with items ["someValue", "anotherValue"] in any order
but: no item matches: "anotherValue" in ["someValue"]
One can discuss which one of those is easier to read, but once the assert fails, you’ll get a good error message from assertThat, but only a very minimal amount of information from assertTrue.