How successful was Medicaid in the 1960s and 1970s?

Medicaid was signed into law as Title XIX of the 1965 Social Security Act, along with Medicare.
At its heart, Medicaid covers a set of mandatory healthcare services for the elderly (who are the primary recipients of this aid), the disabled, and low-income families with dependent children.
Unlike Medicare, Medicaid is administered by the states. However, it is funded by both the federal and state governments.
In the 1960s and 1970s, Medicaid also allowed states to offer optional coverage for Intermediate Care Facilities (ICFs). ICFs primarily catered to individuals with mental disabilities. In 1972, Medicaid allowed states to provide optional coverage for children under twenty-one in psychiatric hospitals.
The next year (1973), Medicaid permitted states to let recipients of Supplemental Security Income (SSI) return to work and retain their Medicaid benefits.
By the numbers, Medicaid was largely successful in providing healthcare coverage to the indigent in the 1960s and 1970s. When the Medicaid program began in 1966, four million people enrolled in the program.
In the first year Medicaid went into effect, twenty-eight states participated in the program. By 1973, Medicaid enrollment rose to seventeen million people. All in all, Medicaid enrollment expanded exponentially in the first six years of the program.
The success of the Medicaid program was effectively facilitated by the increase in both mandatory and supplemental (optional) coverages.
By extension, health spending in the United States rose from 1966 to 1973. Specifically, between 1966 and 1973, overall health expenditures rose from 10.2 percent to 13.5 percent.
To summarize: an increase in healthcare access by previously marginalized populations was responsible for rising Medicaid enrollment and federal healthcare expenditures.
So, Medicaid was successful in the 1960s and 1970s in that it lowered the ranks of the uninsured among the elderly, low-income families, and the disabled.
https://aspe.hhs.gov/basic-report/understanding-medicaid-home-and-community-services-primer

https://www.cms.gov/About-CMS/Agency-Information/History/Downloads/Medicare-and-Medicaid-Milestones-1937-2015.pdf

https://www.cms.gov/Research-Statistics-Data-and-Systems/Statistics-Trends-and-Reports/NationalHealthExpendData/Downloads/HistoricalNHEPaper.pdf