TL;DR: Many Slavic languages don't use diacritic marks. For example, modern Russian and Ukrainian.
I admit I'm expanding your question a bit, but I hope I have good reasons to do so.
First of all, although the marks look suspiciously similar, we should not mix them because they differ by their function:
- Apostrophe in English possessive is a punctuation mark. It is not a diacritic mark since it does not affect pronunciation. Instead, it lets the reader not to confuse plural over the possessive;
- Diaeresis (Hiatus), often used in Romance languages of Europe, is used to force reading two symbols separately, not as a diphthong. One of the most common examples where it could be suitable for English is the word
oo can be misread as
- Umlauts are yet another class of diacritic marks. Their goal is to modify pronunciation of the vowel or a consonant. These are very language-specific. For instance, in German the umlaut over a vowel would make it centralized and/or lowered;
i has a dot over it for purely scripting purpose: it was hard to read it from the Gothic script of 14th century;
- Stress mark looks like an apostrophe, but used to resolve ambiguity of the stressed syllable in a word;
In this context, Russian
й do not belong to any of the groups above. They represent independent phonemes, a palatalized
[o] (as in English word
York) and a palatal consonant
[j] (as in English
may), correspondingly. Considering above, they can't be considered diacritic marks.
There are also examples in other languages: Spanish
ñ is often treated as an individual consonant, not a modified
n, and the same applies to Swedish/Norwegian
We also can find that almost no language is 100% phonemic. In other words, there's no one-to-one correspondence between the phonemes and graphemes.
However, due to historic reasons, this gap was treated in different manners for different languages. In English, it lead to huge differences of how the words are written and read.
[tɪə] (noun as in
[tɛə] (verb as in
to tear off).
If it happened in another language like French or German, one of these words would most certainly obtain a diacritic mark.
- English "suffers" of the same inconsistency between phonemes and graphemes as other languages do. However, historically, this inconsistency has been rather ignored than resolved grammatically;
- There are languages like Russian that also ignore this inconsistency and hence are not using diacritic marks;
- Again, absence of diacritic marks doesn't magically resolve the ambiguities above.