Mozilla only announced that they're abandoning efforts to build the lowest-end stuff. IIRC, most FirefoxOS handsets are still pretty low-end, and have been doing reasonably well.
And feature phones are still dominant in places like Africa and South America, particularly due to their lower cost and power consumption (smartphones are still unable to reach the battery lives of even dumbphones from a decade ago, which is an important consideration in environments with limited/inconsistent electricity). Even in "developed" countries, feature phones are popular with the elderly and disabled, since they usually feature physical buttons that are easier to work with (better tactile feedback, easier to find with poor vision, etc.) and have simpler interfaces.
And feature phones are still dominant in places like Africa and South America, particularly due to their lower cost and power consumption (smartphones are still unable to reach the battery lives of even dumbphones from a decade ago, which is an important consideration in environments with limited/inconsistent electricity). Even in "developed" countries, feature phones are popular with the elderly and disabled, since they usually feature physical buttons that are easier to work with (better tactile feedback, easier to find with poor vision, etc.) and have simpler interfaces.