stanbr: Nice website for Smart Tours. They offer several at very reasonable prices. Maybe the OP can get away with not needing a car and still experience some traditional areas and local businesses most would not normally know about.
I took the bus to Reythmno with no problems, very inexpensive and had a nice day trip there.
Also took a Jeep Safari into the White Mountains which were spectacular, went through the Therisos gorge and stopped at a mountain taverna for a wonder lamb souvlaki meal with a Cretan Salad, desserts and lots of Raki!
Lucked out one night with a Raki-Making Festival along Chania's Waterfront. What a blow-out of a party with live music, local dances dressed in traditional costumes, roasted potatoes, cheese, roasted peanuts and all the Raki you could drink . . . Wow!
Lots to do in Crete and since it's Greece's largest islands you could spend weeks if not months discovering what it offers.
I'm thinking Crete again for 2021. I know it's still 2019 and I'm going to the Peloponnese for Oct. 2020 but one of the most enjoyable things about planning a Greek trip is the research and discovering from travelers like you what's out there.
Very tempting advice from RS members and others.
Loved your trip report on Crete and obviously one doesn't always need a car but it may be OK for a few days to get to those areas the bus doesn't.