I have a contrarian view on this issue based on our extensive travel and on talking with as many expats as possible. Rule number one for whether a retirement locale is going to be deeply fulfilling, it seems to me, is whether you (or both of you if a couple) have at least a few truly close friendships and a sense of community. That applies whether retired here or overseas.
This is even truer in cultures you might think less foreign. I've seen several people with the means to do it move to villages in Tuscany or the south of France and even with fluent language skills they have no chance of penetrating those cultures. Great places to visit, tough places to live. Mexico by comparison is easy, Thailand much harder but at least there you know from the outset that your skin color alone guarantees you'll never be anything but an outsider.
It might be appropriate to give the expats a bit of a break. Part of the issue with "going native" is that your new neighbors will always be a tad suspicious of your short-timer's carpet-bagger attitude and your possible lack of commitment. They have lots of family and local ties, while all of yours may be elsewhere. What's keeping you in their community? What if you have to care for your aging mother, or help out with your sister's kids?
We see it time & again in Hawaii. The most notorious example is McAfee, who made a big splash on Molokai with his promises to help the local community. A few years later he'd abandoned the island and his real estate was up for auction. (Admittedly his behavior was a bit extreme by anyone's standards.) Murdoch is not exactly making friends on Lanai with his tourism and alternate-energy plans. "Eccentric" Japanese billionaire Kawamoto continues to neglect his Kahala real estate, much to the frustration of his neighbors. Even "good guys" like Pierre Omidyar and Tom Fargo are viewed with caution due to their ability to influence the local politicians, businesses, and non-profits.
A submariner turned realtor who's been here since the 1970s told me that he prefers to hire veterans for his agency. They all swear that they want to spend the rest of their lives here, and some of them even retired from the military to stay here. Yet 10 or 20 years later they're moving to the Mainland to live near their grandkids or to take care of their aging parents.
I'm not sure why, but some musicians tend to blend in here quite well. Exhibits "A", "B", and "C" are Mick Fleetwood, Willie Nelson, and Jimmy Buffett. (True, they're not full-time.) But that doesn't work so well with all musicians. Maybe it's musical style, age, or gender.
Even after 20+ years here I may no longer be malihini but it's a stretch to consider that I'll ever be "local". I've lived in Hawaii longer than I've ever lived anywhere else but I'll never be kama'aina. Even now I have to occasionally think about where I'm going to be that day and what style of clothing I'm wearing so that I fit in. (I'll probably keep my ponytail as long as I can twist a scrunchie into it.) For example it's not a good idea to wear "Oahu" t-shirts on neighbor islands, and many old-timer North Shore surfers don't think there's anything funny about black shorts or "Da Hui". I don't wear military fashions like command t-shirts or Navy ballcaps. I only wear my USNA ring if I'm going to be in a roomful of ring-knockers.
Maybe starting a local business or charity would help expats reassure their new neighbors. Perhaps owning a home (where possible) and considering it their primary residence. I think the only way an expat could be truly accepted in the community would be marrying a local followed by sending their kids to local schools. Even then the local spouse would be viewed with a slightly skeptical attitude for their transgression of marrying an expat...