Tiam,
all it takes is one or two buddies to make life much more enjoyable. You're old enough to join the local chapter of AARP, for instance. Here they have simple events like going to the movies together. Even sitting in a theater watching a film together with the option of a coffee before or after is a nice outing.
I'd also suggest Meetup.com As others have said, online is where it's at these days and even trying a few get-togethers would be more activity than you have now. A book club, a pottery making class, or auditing a local college class. May be corny but it does work.
And I don't know your living situation but there are a number of 55+ senior only apartments here in the metro Phoenix area. I've heard many stories of people who initially reluctantly moved into them only to find they really enjoyed being with others their age. You naturally start socializing at the pool, or in the mailroom area, or laundry room, etc. It's not forced, but they find themselves making acquaintances and then friends.
There's plenty of other introverts out there, just take the first steps and you'll be glad you did.