Flavor in avocadoes gone forever?
You're exactly right in figuring out that part of the problem is having grown up with some of the world's best avocadoes, and then moving up North where decent avocadoes are scarce!  :)  Tasty avocadoes aren't all going the way of the dodo just yet, but you might have to move to Texas or Florida, or check some Mexican markets in your area, to get better avocadoes. 

My husband lived in S Calif. as a child. He is an avocado connoisseur like you, as a result. Some of the best S Cali avocadoes are 'Fuerte' variety, which is more flavorful and creamier than Hass. We live in Texas and we get some very good, tasty Mexican avocadoes here- which by the way, are Hass. 

But every single avocado I've brought home to hubby, whether from Mexico, Chile, Florida, Arizona, the Caribbean, Hawaii, Guatemala or Peru, ends up being compared unfavorably to those great S Calif. avocados he remembers. We visited a relative in the S Calif. area about 4.5 years ago and hubby had a delicious, fresh S Cali 'Fuerte' variety avocado during that trip--an avocado which he still recalls most fondly. 

Personally I tried that same S Cali 'Fuerte' avocado too on that trip and while it was a bit tastier than the Hass avocadoes we currently get in Texas, I didn't find the flavor all THAT much better!  But hubby did prefer it a lot; he likes what he was raised on. Also his palate is more sensitive to bitterness than mine and 'Fuerte' is less bitter than Hass.
In recent years, Calif. drought has made the delicious Cali avocadoes, especially the 'Fuerte', nearly impossible to get. 

By the way- I lived in Illinois for a while. That state has the same avocado problem as Massachusetts: too far away from where good avocadoes and other tropical fruits are grown, to get avocadoes with decent quality. Whatever does survive the shipping journey that far North is usually picked much too green. Around the holidays such as Christmas and 16 de Septiembre and 5 de Mayo etc., there was ONE Mexican food store in Chicago that got some fresh, air-flown ripe Mexican avocadoes for sale just for these special days..at $5 each!  

Mom who was raised in Texas was desperate for a good avocado because they are almost nonexistent in Chicago, so she bought 2 of those $5 avocados for Christmas dinner and said it was worth it. I had a small taste in my salad, it was great but geez $5 a piece LOL! I'm real glad we left Chicago and moved to Texas soon after that!

I wouldn't count on S. California's avocado crop doing well anytime in the near future, as that area is likely to only have worse and worse water shortages and drought problems as time goes forward. 

So perhaps, sadly, the 'Fuerte' avocadoes and the other delicious S Cali avocadoes you were raised on are going the way of the dodo. I hope not because they are very good avocadoes and it's always nice to be able to get USA grown tropical fruits. But unless some amazing advances in water and climate management are made to save the Cali avocado farms from extinction, your delicious S Cali grown avocadoes may become nothing more than a fond memory.