Most of this mockery is based on misunderstandings that overgeneralize what the EU is asserting and overlook what most other countries assert.
Most countries have some laws that under some circumstances purport to apply to foreign non-citizens located outside the country, not just the EU.
A key example is defamation law. If you are a Brazilian citizen located in Brazil and you specifically target publications online to UK or Canadian or US audiences in ways that are viewed as defamatory in those jurisdictions, you could very well get sued in those countries' courts, and there are absolutely cases where those courts would uphold their jurisdiction based on the specifically targeted publication.
Similarly, when asked to decide if they have jurisdiction to enforce local consumer protection law against a foreign defendant, the courts in the Canadian province of Quebec will consider whether the foreign defendant has tried to target Quebec consumers, should know that it has ongoing substantial sales to Quebec consumers, et cetera - not only whether it has a business establishment in Quebec.
Conversely, if you are a hotel in New Hampshire, USA and someone located in an EU country visits your US-based English-language USD-only hotel website and books a room for their upcoming visit, the GDPR probably does not apply, since there is no attempt to target the EU. Among other exceptions, the conclusion could be different if the hotel website allows bookings in EU currencies or languages (not counting English and maybe not US/Latin American Spanish because of their use in the US), since that shows an intention to target EU visitors.
If merely being foreign allowed EU-focused businesses to avoid the GDPR, that would be an extremely huge loophole, and EU businesses would make deals with those foreign businesses to shift as much as possible of their data processing stream outside the scope of the GDPR. It would pretty much swallow the whole law. It's not a viable approach.
Similarly, monitoring the behavior of visitors in the EU can also lead to the GDPR applying, since otherwise EU businesses would pay foreign businesses to track their visitors on their behalf, doing whatever legal ownership transfer shenanigans they have to in order to make that work. ("Oh no, this is not a European-owned website, it's an American website to which we've licensed our brand content and which shares 99% of its subscription and ad revenue with us as their license fee... they are allowed to track you even if we can't...")
Of course, you're quite right if you view it as a mockable idea that the EU would be going into foreign countries to bust down doors and collect fines from foreign businesses. Just as clearly, they aren't pretending they can do that.
But if a foreign company does get assessed with a GDPR violation fine in the EU, it certainly gets harder for them to continue to engage in business dealings with anyone in the EU without that fine becoming more possible to collect - and in some cases there are established mutual legal assistance treaties through which EU countries can get foreign countries to help with collecting a judgment outside of the EU.
My guess as to why these non-EU companies prefer to block the EU instead of comply with the GDPR is simply that they don't view the risks of being found in violation as worth the benefits of the additional audience - not because they would necessarily be found in violation. Most of the local news channels would probably not be found in violation if they excluded visitors in the EU from behavior monitoring, but many of those sites don't consider it worthwhile even to take the risk.