I can expand on this problem in a bit more detail, but it comes down to one key term: cost of acquisition.
There are only so many ways that a website can improve traffic flow. The best is if the site somehow goes viral since this is nominally free. This is a longshot and not likely to happen.
There are places where you can share your site/app with a receptive audience. FB Groups, Reddit, IndieHackers, ProductHunt, and even Hacker News comes to mind. Whether it works or not is somewhat dependent on the audience of the property. For example, travel apps aren't particularly popular with the HN crowd, but my app was on the top of r/InternetIsBeautiful for a full 24 hours and my initial batch of users came from r/TravelHacks. These are good for "bursts", but hard to sustain because you can't just keep posting to r/TravelHacks or HN with the same link.
Then there are paid ads on various ad networks or through content creators. These can be quite expensive and often, the cost of acquisition for a single converting user can be quite high! In the early days, this may not be feasible, especially as you're still trying to figure out your audience. One of the startups I worked at had a CAC over $100 via Facebook ads (!!!), but the product was such that they would make it back in 3 months of a user subscribing; the basic math worked as long as they could retain the user.
Then there's SEO. Effectively, this is "free" as long as you can do it well since you'll naturally show up in the resultset for given search terms. Because so much of our user interaction with the web has been initiated from search, this is one of the few things that can be done to improve traffic and visibility. (I think this is changing with generations and with ChatGPT; younger generations may initiate their web journey through a social channel rather than through search.)
TL;DR: SEO isn't a "silly strategy"; it can be one of the most cost effective ways to get visibility because the cost of acquisition is cheap and works well over a long time scale compared.
Absolutely, "SEO" makes me cringe.
SEO should be considered as a bare minimum amount of effort to increase discoverability. Some sites get most of their traffic from social media, so they don't need to optimize for search.
Technical SEO: The on site stuff with relevant keywords in copy, heading/HTML structure, metadata, alt tags, etc. This is all stuff a good site should be implementing by default, but sadly a lot of them aren't.
External SEO: Link building. Getting attention from authorative sources so people know about your work and link to it.
In theory, a site that does these two things well should be better than a site that doesn't.
The problem is that while they correlate to a site having useful content and being useful to humans, they don't require it, especially when Google's systems are too stupid to tell if a site's content is any good and the company is deathly allergic to the idea of hiring people to check or applying any real penalties for wrongdoing.
So SEO is associated with all the crap sites that do these things badly in an attempt to do well in search, and Google's failure to filter them out (perhaps because it isn't actually possible to do so automatically).
It was free traffic. I'm not selling anything, but if I were, it would be costly to funnel them in via FB ads and such. It does pretty damn well for what's basically a crude net. For this channel, I'd imagine getting even second page on Google would be insane.
A lot of the optimization was increasing website speed and not backlinks or whatever.