If I'm not mistaken, the Ecclesiastical pronunciation doesn't distinguish long and short vowels, and people who use it understand the text just fine. Although they do have to memorize where the stress goes (e.g. videre vs. facere), but that basically comes down to memorizing whether a single vowel is long or short (and only for certain kinds of words), so it's much easier. In fact, I assume that you could even ignore stress without hampering your ability to understand the text.
There are some words that distinguished only by vowel length, e.g. nominative fama, ablative famā or present venīmus vs. past vēnimus, but unless you're reading a text where macrons are used (and my experience is that these are rare outside of material for beginners), it'll be context that decides in this case both whether the vowel is short or long and which word it is.
On the other hand, if you do think that down the line you'll want to know the vowel lengths, it's much easier to learn them from the beginning, instead of learning them afterwards.