@Anthroz531 You mustn't have done something correctly because the workaround should work for anyone. For starters the game will never change a build into a community venue like you said, unless we're talking about the Generic glitch itself. You can also buy ANY venue as Retail, be it community or residential, finished or unfinished, as long as nobody is living on it.
1. Load up any household and have them buy the problem lot.
2. Upon buying you will be then transported to the lot. It shall be set to Retail no matter what it was beforehand.
3. Buying it as Retail fixes the Generic issue but you will not be able to change the lot type while you own it (similarly how you can't change the lot type of a residential house with sims actively living on it)
4. Sell the lot on behalf of your household. This will then enable the lot type changing.
@crinrictI had it happen again with this lot. I built about 75% of it in one Save (an old building Save), then saved it to my library and dumped it in my main Save to finish. Shortly after I noticed it was changed to "Generic" from "Bar". Originally I mentioned I thought the glitch is tied to placing lots of 1 type on top of old lots of a different type, but that wasn't the case here because the old lot was a "Bar" just like the new build. I had to do the buy-as-retail acrobatics again to change it to "Bar". It also so far has affected 3 community lots in my game, never residentials, which leads me to believe that perhaps if you manage to enter Live Mode with the lot unfinished (as in it doesn't meet all venue requirements because you're not done building), the game accidentally tries to change it to "Generic" since "Generic" venues have no requirements, and then the whole lot glitches.