Maybe by contrast to other Germanic languages, but I think it’s got kind of a lot compared to most languages. A four-consonant cluster isn’t unusual in English. Though I can’t think of any English four-consonant clusters where three out of four consonants are plosives.
Four consonant clusters? I can only think of words with three, like strengths.
rhythm? if u count the y?
If we’re talking phonology, then the y is definitely a vowel. That would have only a two consonant cluster: thm (the th is one consonant phonetically).
Now I want to play Scrabble™.
Yep. There certainly are English words like ‘prankster’, ‘bootstrap’, ‘constrain’ and even ‘postscript’, so it seems I was wrong. Maybe the difference (as far as Indoeuropean languages go at least) has more to do with precisely what clusters are allowed where in the word (initially, medially or finally). It seems that Russian words can begin with the cluster ‘mgl-’! (‘Mgla’ means ‘mist’ in Russian, apparently.) In Swedish I think that could only occur medially in compunds (like ‘Hemglassbil’).