A lot. A good analogy is modern sailing ships; they're all pretty similar at the end of the day. A modern racing vessel may have a crew of 12 or 15 people, all moving in closely choreographed actions to maximize speed to destination (called VMG "Velocity Made Good" in modern parlance). Each person has a specific job (helmsman, navigator, tactician, jib trimmer, etc). However, outside of racing, any ONE single crewmember could easily sail the vessel across a harbor all by themselves. They could leisurely do all or most of the jobs all by themselves. It wouldn't be a fast trip. It wouldn't be the ideal course. Most likely, only one sail would be used, or maybe only half of each sail would be used.

Likewise, in tall ships with a crew of 100 manning 30 sails, a crew of 10 experienced sailors would have little difficulty making way. Most sails would not be used and the going would be slow. In certain circumstances (e.g. trying to sail against a 5 knot current) with limited crew the ship might not be manageable; the original destination cannot be reached. However, the question "we just lost 90% of the crew; can we safely and intentionally make landfall somewhere?". The answer is yes. Yes, an experienced crew of 10% can sail any ship to somewhere safe, assuming there are no irregular outside sources hindering their passage (e.g. can't outrun hurricanes or attackers, if taking on water, don't have manpower available to man bilge pumps, etc...).