Lots of people writing their own data structures and libraries should be a reflection of the different needs and diversity of the ecosystem, but if it's a reflection of difficulty then it tends to lead to a much narrower ecosystem.

That isn't to say a narrow ecosystem is necessarily bad, it can often be good if a particular language is used for a specific domain as all the libraries and data structures will likely be a better fit for your problems. Going outside of those constraints can often be very punishing in those languages though.