prime256v1 (NIST P-256), secp384r1 (NIST P-384) and secp521r1 (NIST P-521) have been deemed insecure as per Daniel J. Bernstein's research (https://cr.yp.to/newelliptic/nistecc-20160106.pdf, https://safecurves.cr.yp.to/).
Despite that, the adoption of X25519 is too slim. Limiting to that curve would mean dropping compatibility with Safari, Edge and Internet Explorer.