I think something that might help give an idea of the magnitude of the problem are some numbers. Thankfully, just using the 10k tools, we can get an overview of question closure here on Meta SE. Someone with SEDE skills might be able to showcase the issue more broadly (perhaps over the course of the last year) but this does provide a recent overview.
Stats
At the time of this answer's posting, over the last 3 months, 1798 questions have been asked. Of them, 1051 of them were closed for some reason or another. That's a 58.45% closure rate. That feels pretty high, but we do get quite a lot of duplicate questions here (218 for these 3 months, to be specific), so I'll let that slide for now.
Of those 1051 questions that were closed, 710 of them were closed with our "Not about the software that powers SE" closure reason. That's 67.55% of questions closed in the last 3 months, or 39.4% of all questions asked in the last 3 months. Of those 710 questions that were closed with this reason, only 2 of them were reopened.
Now, I should note that we had winter-bash-2022 occur within the last 90 days, so I highly suspect that this data is actually reflecting less than the normal question closure percentage, but I don't imagine it's by that much.
Based on these stats alone and barring other activity, there's a 40% chance that the next new question you see posted on Meta SE will be blatantly off-topic.
Why are you throwing stats at me?
I should be clear, this isn't really that concerning for the denizens of Meta. I wasn't around for when, as Shadow says, we had floods of off-topic questions, which certainly would be a drain on moderation resources, but... For now, users with close and delete-vote privileges frequently help to close and delete these off-topic questions. Moderators and CMs will also help out rather frequently, both with closing and deleting these. There's not really a big drain on moderation resources here at present, though it should be noted that Glorfindel created a whole userscript designed to help quickly execute related moderator actions on blatantly off-topic questions, which might speak more to the problem. I've even seen some users suspended with the reason "for asking programming questions on Meta".
What concerns me more about this is that for a new user, this is really confusing. From a newer user's perspective, you've asked a question through a page that looks normal (even if you've got a bit of banner blindness), typically earnestly trying to get an answer to your problem, only to be met with question closure, deletion, and typically a comment explaining that this isn't the right place, along with a link to the All-Sites page and some links to various help articles. I just... I don't feel like that's a good experience for a user who's clearly lost enough that they posted on this site in the first place.
The design of the question page can do better. It hasn't changed since ex-Community Evangelist Tim Post pointed out that it needed improvement, and it's been confusing new users ever since. I don't expect a design change to make this problem disappear entirely or anything, but the least we can do is make that page a little bit more clear about what's on-topic here, and indicate where a user might find a better place for their question if it's not.