My guess is, it varies wildly from person to person.
Some people could be just naturally very gifted. Paul Morphy, for example was.
And also what is considered taking chess seriously will vary wildly. Some consider taking it serious if you play every week and even care at all about improving. Others will not consider it serious unless you spend all your available time on chess…
So my guess is, it is impossible to say.
i've been playing chess casually since the pandemic, and try to play at least a few games a week. it's a fun hobby for me.
i don't think i'm interested in memorizing lines, learning theory (beyond basic stuff), studying games, taking lessons, playing games longer than 10 minutes, or devoting more than maybe an hour a week to this. i am, however, interested in developing an appreciation for the bigger principles and concepts that make the game fun and interesting.
at my level (1400) i'm still blundering major pieces constantly, as are most of the people i play. i assume those errors disappear as one approaches 1600s, but after that i'm guessing i won't be able to get much further without actually learning some stuff?
how far can you get without taking the game seriously?