Is 10-year-old information from this website worth anything at all? [closed]

In short: Yes it is worth something.

The long answer:

While there are certainly things that are done differently/better now and we do need a system to update those Q&As (E.g. Somehow un-accept an outdated answer to question where the correct answer has changed.) There are still a lot of question & answer that remain relevant and things should not be removed, only because they are old:

Basic hardware question

How physics works does (luckily) not change, so many post covering hardware stand a good chance of being relvant ages later. Take What is the purpose of the holes marked "Do Not Cover" on hard drives?

Basic software questions

One of the highest scoring question on Superuser ever is: How can I sort the output of 'ls' by last modified date? Given how fundamental the ls-command is, the answer is not going to change anytime soon.

Old products still in use

Especially in professional environments, where e.g bureaucracy causes slow change one can get stuck with what would be considered outdated soft/hardware. In that case the answer to an old question is still "current" to you.

Manufactures like HP might stop providing support, documentation or even drivers for older models, making the posts here all the more important.

You are right in that there is frustration when getting outdated answers to current questions. It should be possible to better filter/categorise specific solutions for specific versions/situations. On Stackoverflow there was the discussion once about creating version-sub tags but that never produced anything.

If you have any idea on how to improve the current design/search/content-curation do share! This is an area that still needs improvemnt. You can also help other by updating/adding new answers if you happen to notice something is outdated or you know a better way.

Why is this website giving out decades-old computer information ...

Because decades old information sometimes still applies and therefore automated pruning would delete useful information.

... as if it were current.

In some cases people who contribute answers don't explicitly mention product versions etc that would help viewers see whether the problem or answers apply to current versions. This is human nature.

When is this site going to delete its ancient articles that don't apply to anything anymore.

When ordinary participants like you or I, mark the articles as obsolete. You have the same rights and responsibilities as any one else in this regard. For some actions, you do have to contribute enough to demonstrate that you are likely to be a careful responsible contributor. You don't need anyone else's permission though

You should feel free to carefully add up to date answers, modify old question or old answers to add version applicability etc and generally improve things.

When doing that, I would try to respect the generosity of the original contributor.

Completely frustrating and totally useless website

The popularity of this website and my own experience suggest to me that it is often useful.

Other Q&A websites exist though if you feel otherwise after calm reflection.