Yeah, security through obscurity as part of securing a system is good. Security through obscurity as the only way of securing a system is not.
Like, a lot of it comes down to 'high friction' vs 'low friction'. Obscurity means high friction. It means that the attacker needs to craft a specific solution for your site or system in particular rather than relying on an off-the-shelf solution to handle it all for them.
For example, the article's point about changing the WordPress database prefix fits into this category perfectly. Does it really make things that much more 'secure'? No, of course not. But it does mean that automated scripts that just assume tables like wp_posts exist will fail. It means that an attacker can't just run any old WordPress hacking toolkit and watch it do its thing, they have to figure out what database prefix you're using first.
Same with antispam solutions. The best solution to stop spam is to make your site unique in some way. To add some sort of challenge that a new user has to overcome to use the site, like a question related to the topic, a honeypot field they can't fill in, a script that detects how quickly they register, etc.
This won't stop a determined spammer, but it will stop or delay bots and automated scripts that rely on the target system having the same behaviour across the board. The spammer has to specifically target your site in particular, not just every forum script running the same software.
And much of society works this way to a degree. A federated or decentralised system (whether a social network or political movement) isn't technically harder to attack than a centralised one might be.
But it is more work to attack it. If a government or company wants to censor Reddit or Discord or YouTube, they have one target they can force to censor information across the board. If they want to target the Fediverse or some sort of torrent based system, then they have to track down dozens of people and deal with at least some of those people refusing or taking it to court or being in countries that aren't under their control or whatever else.
That's kinda what a good security through obscurity setup can be. You can't mass target everyone at once, you have to target different systems individually and spend more time and resources in the process.
However, you still need real security measures there. Security through obscurity is like hiding a safe behind a painting. It'll stop casual attackers from finding it, but it won't stop a targeted attack on its own. You need a strong lock, materials that are difficult to drill through and the safe itself being difficult to remove from the wall too.