“I’m not good with change,” people announce when confronted with the new. But two L.A. arts institutions had better get used to it: The Huntington Library, Art Collections and Botanical Garden said goodbye to president Steven Koblik, who retired last week after 14 years. Mike Boehm assessed Koblik’s role in what one observer called “an explosion of vitality” at the San Marino organization: new buildings, extensive renovations, expanded gardens, and an increased interest in what museums call “the visitor experience.”