It is a very good question...
The only thing that I can say, is that the majority of people will universally recognise and accept when something looks good - regardless of whether it is faithful, or how they pictured it in their mind.
I mean, sure, most of us before we have any clue what the suit is going to look like, will express what side we are on (traditional or modern). But it's not going to make it impossible for us to appreciate a costume that looks good, even if it doesn't fit our mind set image. Equally, anyone will admit when something DOESN'T look good too.
For instance:
Traditionalists still hated the SR costume. It is MUCH more faithful than this new suit... but it didn't look good. It looked plasticy, the t-shirt collar and cape attachment was horrible, the belt, the maroony colour, the boots... how the entire team behind designing it didn't see it looked bad is beyond me, because the majority of fans knew it looked nothing close to cool.
Modernists (I know, I know, not a word
) as well, still hate the Burton concept design. Because it is hideously ugly, despite it being a modern concept.
Now we have this new design. Not faithful in every way, but not modern in every way either. It has a great open neckline, cape attachment and boots. We have a style of 's' that is reminiscient of past 's's but not the most recognised version. We have a colour scheme that reflects the opposite of SR's (dark blue, brighter red), we have no 's' curl (so far), and last but not least, we have no trunks.
Beyond that even further, we have a silver pattern design in place of the trunks. Something we have never seen before.
And all the majority of us can say is that it works. It simply is what no other Superman costume design has been before - it's cool. It looks good.
I know a lot of it is down to the man in the suit. I really really don't think i'd have liked it as much if i'd seen Routh in it first.
But mostly it's just because the design is sweet. Period.
TBH, as a girl, I see nothing funny about the crotch... It's enough to make any girl blush