Yeah, the standard should have just specified like a sha256 HMAC, when that becomes broken in 20 years we can just do a JWT2 (or invent some new successor standard)

given that md5-hmac isn't even broken despite md5 being broken, it seems unlikely sha256-hmac will fall in 20 years.

that said, algorithm agility isn't the primary issue, its whether you want symmetric (hmac) or asymmetric (digital signature). Both have advantages and disadvantages so there is no per-se right answer, it depends on context.