It fall out of fashion, along with Pascal, Perl, Ruby, but that's just fashion.
How can a language be "inefficient"? You can say it lacked on expressiveness. Maybe was too verbose? But I would not place BASIC into the "verbose" category.
I don't have to relearn natural language every 5-10 years, but for some reason I'm expected to when it comes to programming.
Because BASIC simply doesn't have first-class functions, and they would be quite hard to represent in a BASIC-like syntax while keeping the language idiomatic. Even the unreasonably clunky C pattern of having a pointer to a function taking void* as its first argument (to account for closure captures) gets you a whole lot closer to functional programming than even the fanciest BASICs.
https://learn.microsoft.com/en-us/dotnet/visual-basic/
https://www.mikroe.com/mikrobasic-pic
Just the three that come to my mind, of BASIC toolchains that people actually pay real money to use.