all of humanity should be recipients of the wealth that taxation of shipping lanes and exploration of natural resources under the sea's surfaces offer, not just 1 nation.
Exactly - not just the USA, and China isn't taxing any vessels passing by - but only those that port in China. It's called import tax.
China has innumerable times offered it's neighbors, who don't have the investment capability nor the technology to jointly explore natural resources - effectively undermined by the USA.
As such e.g. the Philippines can proudly claim a vast stretch of ocean - and don't get anything out of it, whilst China is effectively harnessing resources within it's undisputed waters and sends it's massive fishing fleet, just as e.g. Japan to INTERNATIONAL waters across the planet to harvest. E.g. Canada's and the US West-coast - right down to Chile.
and Cuba was embargoed because they had long-range missile plans against the US.
Cuba
never had any nuke long/mid/short range missiles stationed. see "Cuba Crisis" and the USA therefore has no right whatsoever to embargo and sanction Cuba since 61 years. !!
i don't see Taiwan or any of China's other neighbors in the SCS do that.
Do what? intruding? taking resources?
Get some spectacles if you can't see it, ALL of them Taiwan, Vietnam, Indonesia, Malaysia, Brunei, Philippines, S-Korea and Japan are constantly intruding into others claimed waters, fishing and gas&oil-rigging - and trying to expand their respective claims towards each other - the PRC 9 dash line, aka the Taiwan 12 dash line, derives from the KMT (ROC) and they are up-keeping that claim.
And the USA until today - since 1934 (ROC) has never refuted today's Taiwan's claim - that factually is larger then that of the PRC, since it includes 3 dashes that Mao gave voluntarily to Vietnam. Taiwan has also rejected the international courts ruling in regards to the Philippines.
Why isn't the USA a signatory to UNCLOS? because they uphold numerous illegal and disputed claims themselves, that would backfire onto them, if the USA would sign UNCLOS.
The USA is simply trying to prevent the economic rise - thus also the military rise of the PRC - with all means. Such as lying their heads of since 2014 on a daily basis - soon 10 years, about China going to attack Taiwan tomorrow.
What is the difference between China's "artificial" bases resting onto atolls and those of e.g. the Philippines?
China has the $$ to build huge bases incl. airstrips - whilst the poor Philippines have to make use of a naval shipwreck stranded onto an atoll, to act as their military outpost.
So again: Which INTERNATIONAL organization appointed the USA to be the "custodian" of the South China Sea??