Show is called trigun
Look inside
Protagonist does not have three guns

Keeping original posters' credit intact is cool.

Read somewhere that's because the mangas in the store just show the title at the front. By putting the whole story premise into the title prospective buyers can see at a glance what the book is about without picking it up.

Give it a little time and books will be intriguing again with a mysterious short title.

There is now so much manga and light novel titles that I kinda understand why they do this. It is hard to decide what to even click on, and if I can't even tell what genre it is from the title or cover picture, I'm less likely to check it out

OP left out the Adjective Noun Fred naming convention that lasted from the late 70s through the late 90s

Mobile Suit Gundam

Irresponsible Captain Tylor

Pretty (However they translated Senshi this time) Sailor Moon

Samurai Pizza Cats

Space Runaway Ideon

Devil Hunter Yohko

and on and on and on.

Trying to be unique in a largely crowded endeavor like Japanese manga is a very difficult game. Like choosing names for one's creations. So some authors have to resort to using bewildering longer titles if only to stand out, and it gets weirder in very prolific manga subgenres such as a harem romcom.

I faintly remember about Japanese creatives -- and some businessmen -- trying to find naming inspirations from practically anywhere -- a favorite movie, actor, athlete, an odd quote, a catchy phrase in French or Italian (there is heavy use of "atelier"), etc. -- for which to name their next work, not just manga but Japanese product names and trademarks in general; a girl's fashion brand over there which had taken a "Cecil McBee" as its trademark without the knowledge of the actual musician bearing that name (he was informed of it, got surprised, then tried unsuccessfully to sue in court).

I would read the HELL out of Blood Joe!!!

My favorite animes from the era remain:

Samurai Pizza Cats, City Hunter, You're Under Arrest!

Where can I watch "Blood Joe Dating Two Slime Stepsisters At The Same Time"?

I think that's because they are Korean but I could be mistaken

Hey, give them some slack, they’ve got to stand out among the sea of mediocre titles.

moore's manga law

Others in this thread are close to the truth when they say this is a light novel thing more than a manga thing. The reality is that this is a web novel thing, even before these stories become published light novels. I am going to quote an answer I wrote previously about this:

Long, specific titles have always been somewhat of a thing. For example, did you know that the novel we typically refer to as Robinson Crusoe, published in 1719, was originally titled thusly:

"The Life and Strange Surprizing Adventures of Robinson Crusoe, of York, Mariner: Who lived Eight and Twenty Years, all alone in an un-inhabited Island on the Coast of America, near the Mouth of the Great River of Oroonoque; Having been cast on Shore by Shipwreck, wherein all the Men perished but himself. With An Account how he was at last as strangely deliver'd by Pyrates. Written by Himself."

In modern light novels, the long titles come from the ease with which amateur writers can self publish to a website like syosetu. This causes tons and tons of stories within the same genre or content tags to be listed alongside each other. So, having a long, specific title helps your writing stand out by acting as a quick synopsis rather than having a website visitor click through and read the synopsis of hundreds of search results.

A lot of our modern light novels were originally self published as webnovels to these sites and have therefore inherited the long titles that helped them stand out on those sites. I just wish that the titles would be adapted and shortened as well as they transition from webnovel -> light novel -> manga -> anime. Some of them just keep the long title but pick up shorter nicknames since the Japanese language is so prone to portmanteaus (konosuba, danmachi, arifureta, etc.).

Chainsaw man
City
Dr. Stone
Mao
Goblin Slayer
Spy × Family

Confirmation bias is one hell of a bias.

They got a point.