Your second left parenthesis belongs one line higher. A more clear way to read it is to write out four copies of it, and then in the first copy delete or clauses 2, 3, and 4. In the second copy delete or clauses 1, 3, and 4, and so on. That gives a separate complete sentence for each of the four ways you can run afoul of that section:
A site is illegal if] the U.S.-directed site is primarily
designed for use in offering goods or services in a manner
that engages in, enables, or facilitates...
A site is illegal if] the U.S.-directed site is operated for
the purpose of offering goods or services in a manner that
engages in, enables, or facilitates...
A site is illegal if] the U.S.-directed site has only
limited purpose or use other than offering goods or services
in a manner that engages in, enables, or facilitates...
A site is illegal if] the U.S.-directed site is marketed by
its operator or another acting in concert with that operator
for use in offering goods or services in a manner that
engages in, enables, or facilitates...
YouTube fails to fall under the first because it is not primarily designed to engage in, enable, or facilitate infringing. It fails to fall under the second because it is not operated for those purposes. It fails to fall under the third because although it does get used for the prohibit activities, it has substantial legitimate use. It fails to fall under the fourth because Google does not market it as an infringing tool--indeed, they discourage infringement.
The section that YouTube (and Reddit, and most other legitimate sites with user content) are in danger of running afoul of is the section that says a US-directed site is a site dedicated to the theft of US property if it:
is taking, or has taken, deliberate actions to avoid confirming a
high probability of the use of the U.S.-directed site to carry out
acts that constitute a violation of section 501 or 1201 of title 17,
United States Code
Some think this will requires the sites to put a lot of effort into actively monitoring user generated content and taking down things that might be illegal, as opposed to current law where they have only have to deal with things specifically brought to their notice via a DMCA notification. The section is sufficiently unclear that that is a reasonable reading of it.