It really depends on your dialect (idiolect?). If you are ocker*, kiwi, or yarpie then vowel length may matter because there can be words with the same vowel sound where only the vowel length changes the meaning. English in Northern England also has vowel length rules (although presumably not often confusing since most speakers are very familiar with English as spoken in the rest of the country).

In New Zealand, can’t and cunt have the same vowel sound, and foreigners can make embarrassing or hilarious errors!

Shed and shared have different vowel sounds in my accent (shared rhymes with ear or air - a diphthong?).