In general, no, but some new manga are really bad

imo this is a natural consequence of there being more/easier ways to publish these days. Digital-only publishing has a lower bar, so more stinkers sneak in. However, the baseline for a magazine is the same as it ever was, and a decent number of online works are still incredible, so to say that it's worse "in general" is just completely forgetting about decades of bad manga that no one even cared about. Mediocre-to-bad manga from the 1980s never even got translated so most of you guys have no idea how bad it was.

Survivorship bias makes it easy to remember older manga as "better" because the good (& the amazingly terrible) manga that we read then are the series that linger in our minds. I've read a ton of mediocre older manga over the years, none of which I could tell you anything about, because it was so forgettably dull that that left no impression in my brain.

Yeah, this is a scanlation tracker site, so it's worth pointing out that most people here are reading manga in translation, and manga will only get translated/scanlated if there fan scanlators and/or publishers interested in it. Years ago when there were fewer manga translation book publishers and a smaller community of scanlators, the only series getting translated were the already REALLY popular series, the manga that translators had a personal interest in reading, and/or manga that the handful of existing publishers thought could turn a print publishing profit. There are mountains of mediocre older manga that were never and will never be translated from Japanese because they sucked and nobody cares about them now.

Part of the problem is publishers opening the flood gates and funding way more manga and anime than they used to, so way more bad products get approved.

Another part is that, increasingly, authors don't understand how good literature works: they take the moments they like and reproduce them (sometimes with a spin) without actually knowing why something worked. This means all sorts of issues from plot contrivances to awful characterization, to edge for the sake of edge with no realistic filter.

Another part is that, increasingly, we're on screens and not living life. Miyazaki complained about animators not having enough IRL experiences to create something special and he's been proven right. The best stories seem to be from authors who know how people and places interact with each other. Kind of hard to avoid stereotypes and checklists when you don't know anything but.

I'm also starting to see a moral failing among some new authors (a different way manga overall may getting worse). For example: there's an isekai manga that wants the reader to cheer for rape.

Some publishing agent actually got this funded, apparently.

And no, seeing how bad it got wasn't worth it.

I'm a jack of all trades but master of none. Too many jars and not enough hands.