Edit: I mean you already provided an implementation, no?
julia> abstract type Parent end
julia> struct T1 <: Parent end
julia> struct T2 <: Parent end
julia> has_feature(::Type{<:Parent}) = false
has_feature (generic function with 1 method)
julia> has_feature(::Type{T1}) = true
has_feature (generic function with 2 methods)
julia> for Ti in subtypes(Parent)
@info Ti has_feature(Ti)
end
┌ Info: T1
└ has_feature(Ti) = true
┌ Info: T2
└ has_feature(Ti) = false