HL7v2 was invented in 1989. It was invented to meet the needs of then intra-operability between existing HIS systems. HL7 itself is a open organization comprised of a variety of members from vendors to health systems to life sciences/pharma.

HL7v2's problem is that it is 30 years old and probably should have been replaced by something earlier. Then again, so should most X12, mainframes, COBOL, etc. etc. FHIR is good, but the challenge is that the incentives for interoperability are much lower than those for intra-operability.