el7 is better than el6, but that doesn't mean your 'march' of the moodle is LTS to LTS with PHP/MySQL upgrades at appropriate times before next hops upwards in Moodle and then you are done with it for many/many years to come!
CentOS has an end of life ... and isn't considered to be the same 'LTS' as it was with 5/6 ... when IBM bought RedHat, the Enterprise release of CentOS also changed.
CentOS 7's EOL: June 30, 2024 ... granted that's a couple of years away, but 'time flies' and considering your entity waited soooooooooooooo long to look at upgrading Moodle, am gonna guess the mind set has not changed.
So if seeking LTS ... all the way round, one could be looking at not only a 'march' of moodle but a migration to a different OS that does have LTS.
Make sense?
Like Mr. V's page on Moodle, Google actually offers something that might help:
'CentOS EOL Guidance" page:
https://cloud.google.com/compute/docs/eol/centos-eol-guidance
'SoS', Ken