In modern Israel people speak a modern version of Hebrew. Their modern writing system has no vowel points. The modern Jews understand and communicate just fine with no vowel points. If you grow up speaking a language, which writing system is used for it is quite flexible. It does not necessarily need a system with all the sounds indicated in its writing system.
Language is primarily a spoken phenomenon. There are people who know their language just fine but are illiterate. Since Hebrew has continued without break for centuries, it's always had a intelligible life, with or without the vowel sounds being written down.
Sure, there will be a few instances where words will be lost or confused, as Earnest demonstrates, but the Jews I know do just fine with both modern spoken, and ancient biblical, Hebrew.