The ten second summary impression -

Some amusing vignettes.  However, overall somewhat disappointing.  There
are too many repeated series (KOR, Ranma, UY, SM) and too many of the
characters use gender confusion (Shun, Ukyou, Haruka, Ryuunosuke).  First
season had a better balance and mix of characters.  There are many other
series set roughly in present-day including YUA, Ghost Sweeper Mikami,
Phantom Quest Corp, Gunsmith Cats (I know it's set in Chicago, but I'm sure
that there is some way to get Rally or Minnie May over to Tokyo), Project
A-ko, MB, and DHY.

You want the simple reason why some series were repeated? First
there's continuity. Second, if I decided to get REALLY obscure with
the characters, I could sure as heck have picked any one of a
number of series, but let's face it... who would read that?
The entire point of this second season IS the gender confusion. The
first season characters, with the possible exception of Nuku were all
involved in a multi-person love relationship.

The inclusion of Yotsuya is problematic.  It is funny to see him clueless
as to the real sex of many of his housemates.  However, apart from the
question of why the producers would allow an older man to remain in what is
supposed to be a group of young people,

He bluffed his way onto the show. It was supposed to be Godai. But when the
reviews started coming in, they decide to keep him instead.

there is the addded problem that

Ukyou, Haruka, Ryuunosuke, and Akane would have absolutely no qualms about
sending him to the hospital if they caught him peeping and Yotsuya was
never that discreet.

Perhaps not, but why would he be peeking on 'men'? Especially when Akane
could look like anyone.

-Scriv