Venture capital has been a revolution unto itself since its start decades ago. Its high-risk/high-reward financial model has been so successful in growing revolutionary companies that countries around the world have sought to emulate its operating system and success. Now, VC itself is being revolutionized, as the biggest firms in the space are changing their investment strategies.

For decades the process has been straightforward and operating like a juggernaut — finding, underwriting and profiting lavishly from one blockbuster startup after another, including hits such as Apple, Google, Facebook, WhatsApp, Stripe, Airbnb and an endless array of other success stories.

Now the VC model has come under strain for several reasons. For starters, the cost of building a startup company into a full-fledged powerhouse has increased sharply, and the exit strategy — usually through an IPO or acquisition — has become elongated, leaving investor dollars tied up for longer peri