Here's the deal ... after JLC issued a heartfelt apology for recently claiming Marvel was in its "bad" phase, the "Deadpool & Wolverine" star chimed in -- and reminded everyone Jamie Lee's original quip really wasn't all that serious ... nor did it warrant an I'm-sorry.

Ryan took to X on Thursday amid Jamie Lee's announcement that she'd stop with the "mud slinging" -- with RR making it clear the apology wasn't necessary in the first place.

He seemed to channel his rebellious Deadpool character with his sentiment here, as he wrote ... "Wait, is everyone expected to apologize for slamming Marvel post-Endgame?"

If we're translating this correctly ... Ryan is essentially saying everyone is entitled to their opinion (even ones that crap on Marvel) ... so, people can relax with the pearl-clutching, which is in line with his character.

In fact, we're right on target in that regard -- sources tell us that's exactly what RR was going for here ... namely, channeling Deadpool (who bashes Marvel all the time) in real life.

Of course ... this is still a pretty bold move from Ryan, given he's kind of the darling of Marvel right now. Remember, "Deadpool & Wolverine" has already brought in over half a billion dollars at the box office ... and is on pace to break all sorts of records.

JLC has yet to respond to Ryan's defense of her ... but we're sure she's feeling the love, especially after sparking outrage from Marvel fans across the globe.

Jamie Lee isn't alone in her anti-Marvel stance ... as director Martin Scorsese has criticized the superhero franchise on a number of occasions. Not to mention, Jennifer Aniston, Seth Rogen, Reese Witherspoon, John Cho and other stars have voiced their disinterest in suiting up for Marvel.

Marvel isn't without an A-list roster, however ... as they just brought Robert Downey Jr. back into the fold for an exciting new villain role. So, we're sure they're not sweatin' this drama.