Akismet letting a lot more spam pass through those last months

Hello,

It’s been a bit more than 3 months, more or less, that I’m observing a change in the spam elimination on a wordpress blog. Before that, if there was one spam comment per day that wasn’t deleted without me seeing anything, that was it. And finding the occasional “falsely considered as spam comment” (around one a week) was a breeze.
But now, there are approximately fifteen to twenty spams a day that aren’t immediately deleted, and it looks odd to me.

Maybe that’s normal behaviour, but maybe not? So, just in case, I’m reporting it in the support forum.
But it’s a real bummer, as I want to check spams to make sure no legitimate comment wasn’t wrongly flagged… and it’s a damn painful chore with all that spam passing through ??

I’m not sure if that’s the unescapable normal way for Akismet to work, or if this behaviour, this amount of spam, isn’t anomalous.
May I humbly ask what it is, normal or not?

More details follow:

– The source of the spam: wordpress blog comments. No contact field on site.
It’s a wordpress 5.3, on a Debian Buster LAMP server.

– Possible plugin interactions: wp-discuz is also installed, I don’t think they have anything to do with spam filtering, they’re a polished presentation UI to make the wordpress comments look better, and in their support forums, they say they are setup to work hand in hand with Akismet when Akismet is present on the blog.

– Is Akismet even working: in wp-admin/options-general.php?page=akismet-key-config it says the API key is valid and the status is active.
However, the first time I open that Akismet config page, in a day, the page always takes more than five seconds to load, with occasionally a failure to load the graphic showing the number of spams deleted per month. For last month, it says it deleted 1982 spams.

– How Akismet is configured on the blog: I saved those settings to another screenshot:

View post on imgur.com

Key line: a tick in front of “Silently discard the worst and most pervasive spam so I never see it.”

– The nature of the spam: just look at this screenshot, covering a day’s worth of spam:

View post on imgur.com

– How the detection of the spam is done: the spam is located in the spam folder, not even pending approval, so it’s properly detected as such, normal visitors don’t see it

– In what way is it different from before: until over 3 months ago, there would be 1 or 2 comments in the Spam folder, max. The difference is huge: the recognition of false positives (valid comments by real people, falsely recognized as spam) is no more an easy task, it’s now a chore that requires to scroll through lots of pointless spam lines.

I hope my post covered every possible question.

And basically, the question is: is that normal, such a daily volume of 15-20 spams that Akismet didn’t delete immediately?

If yes, okay, I can live with it.
But if no, well, maybe a solution exists, I welcome all suggestions, thank you very much ??