Were there too many characters in this movie?

Batgirl absolutely wasn't needed. The subplot involving Alicia Silverstone feels like it was shoved in from another script. The scenes in which Barbara is motorcycle racing for money don't really push the plot forward in the greater scheme of things. It comes across as filler and perhaps, Joel Schmuacher trying to make up for the fact that he haven't had an action scene in a while.

Also, the way that she becomes Batgirl makes no sense. I'm not going to go into all of it right now, but we don't get her motivations for wanting to become a superhero. In Batman Forever, Dick Grayson wanted Bruce Wayne to help him get revenge against Two-Face for killing his family. Yeah, Barbara's parents died too, but unlike with Bruce and Dick, they weren't murdered in front of her.

The tone for Batman & Robin was all over the place. Part of it comes across as a self-mocking parody if not hallow, tone-deaf attempt at updating the campy formula from the Adam West show of the '60s. And then, we have more "weighty" stuff that we're supposed to take seriously like the importance of family, teamwork, and trust.

Now that I think about it, Batman & Robin faces the same issues as the Iron Man cartoon from the '90s, at least the first season. Both were seemingly more considered with selling toys (as a matter of fact, I think that the Iron Man cartoon was initially an afterthought as Marvel was more concerned at the time, with getting a Fantastic Four cartoon on the air) than putting a quality product first and foremost:

https://tvtropes.org/pmwiki/pmwiki.php/GrowingTheBeard/WesternAnimation

Like its sister show under the Marvel Action Hour banner, Fantastic Four, Iron Man had a rough go around to say the least, when it debuted in 1994. Simply put, Season 1 of Iron Man was formulaic , bland and actually boring at times. More to the point, the first season's episodes were often comprised of meandering scripts, which were usually needless complex. The scripts were also often crammed with awful, non-nonsensical pseudo-science, bizarre, out-of-left-field dialogue, and ill-fitting humor. To make matters worse, Season 1 of Iron Man contained choppy animation courtesy of Rainbow Animation, lame, out of place CGI , and inconsistent voice acting. But just like with Fantastic Four, Marvel Comics radically retooled Iron Man for its second season. The glut of regular characters was cut down, the formulaic style of Season 1 was discarded in favor of directly adapting popular storylines from the Iron Man comics. There is also a greater sense of continuity as the affects of events in one episode carried over into the next. Another change in direction was Koko Enterprises replacing Rainbow in the animation department. In return, the art became more detailed and moodier and the animation became much smoother. Finally, the mind-numbing opening credits of Season 1 are replaced with a fairly awesome rock theme.