What about the Marvel movies? Marvel comics have decades of continuity that lock out older fans, the movies ignore them and focus on what attracted people. They don't make the mistake of assuming that if they change anything ever at all, the result will not be "what people liked". And they are wildly successful, among existing Marvel fans, and among people who never read comic books.
Which is good, because comic books are absolutely moribund right now. Just like L5R was right before the sale.
While transition to a different media, I agree, then it is best to just take what worked and drop the rest. But if you stay within the same medium, I think a reboot is kinda bad. DC comics did that, multiple times, and I hate them for doing that, since all their character now feel shallow and some of the greatest stories they had are now just a dream, the reboot never can live that down. Marvel did that a little more clever, with their ultimate universe, that didn't simply have thrown out all continuety, since people still could and can read the classic 616 marvel universe. Technically FFG could go with a paralel unverse approach too for L5R, after all with KYD we basically have that option already, but I am not sure how happy people would be with that.