That is not the core of the problem. Spammers are humans, and sometimes
they will solve recaptchas in large quantities to get their spam
through. Its about having a multipronged approach for administrators to
stay ahead of them. For some examples of free solutions see
https://www.mediawiki.org/wiki/Manual:Combating_spam. It's even possible
to connect spamassassin to forms. Gitlab needs tools and automation that
detects and rolls back spam, bans users, knobs to tune restrictions and
rate limits based on how spammers are acting. Gitlab inc just hasn't
seemed to care much to help people trying to use Gitlab and keep their software freedom.