well, McF and DCD weren't really updating Looneys and Hanna Barbera -- they were capturing classic moments in plastic as it were. objective achieved, i believe.
it's also going to work on a case-to-case basis -- for the examples, there's nothing much indelible about the character aside from their now-iconic looks. good thing there's nothing particularly striking about LT or HB that needs to be updated for the current day [more on dialogue and joke content than appearances], so that's safe. those superhero-ish Looney Tunes, though... well, it's something new and unrelated mostly just referencing the old, so i can personally let that slide.

also, the original concepts don't always translate... "80's futuristic" is different from current futuristic, for instance [we don't dress like their then-future 2005 or 2006-era characters do, or drive flying cars, although i wish we did!]. same thing for "this character looks barbaric and tribal" -- diffrrent aesthetic design concepts from then and now. i know i wouldn't mind those redesigned Thundercats, maybe with less of an identifiable 80's look [and articulation, PLEASE -- updated He-Man and TMNT would've been a lot more fun for me if they had that].
i do agree that reinventors, as it were, would do well not to go too far or to reinvent for the sake of it... that rarely works as well as it's hoped to [i'm not too groovy on Jason Todd-as-Red Hood for that reason, although i respect the possibility of good stories from it at least].
- last "sorry for the long-winded response

" maximal