There are not that many people capable of a secure design & implementation. But that is just the tip of the iceberg; any network promising anonymity requires a large number of nodes (and high traffic), and that number must stay significantly larger than the number of malicious nodes that try to deanonymize the network.

Adoption remains a huge challenge (and not really one you solve with technology or skill). It doesn't help that design decisions that improve security can degrade the user experience, leading to lower adoption and lower security. Sigh.