Earlier quoted context omitted.
> "is the beginning of the reason why English is written without accent marks" > sh, th, ee, oo, ou That's cool 'n all, but I believe that only applies to French writing in English for English people. Many languages have combinations of letters that have a single sound, it's no excuse for not having accents. In German one can write strasse and straße or müller and mueller (different writing, same sound). They too don…
> Many languages have combinations of letters that have a single sound, it's no excuse for not having accents. You don't need an "excuse" for not having accents. Digraphs and diacritical marks are simply two different ways to mark a letter as being pronounced as "somewhat similar but different". Whether one is better than the other is a matter of subjective perception, and it's very common for languages to not do it…
about accents, see my examples. they are used to disambiguate, which is a bonus in itself.
> If "ch" always meant the same thing, it would be just fine.
that is my take too: in German you have ss and ß, for historical reasons, but both sound the same and have a predictable pronunciation, always.