You mean in DCD's conspiracy. In fact, kuuga is not weak at all. Only he can stand up and fight DCD again in the Cavaliers War, but it looks rubbish because the plot needs to deal with actors (short people). When you look back at the original Yusuke Godai (not the pirated Yusuke Onodera), you will find that Kuga is much more powerful than DCD, and from the original design, the Anadam stone on Kuga's belt has infinite evolution ability, and it will gain stronger power through Yusuke Godai's own "strong" will and sublimation power obtained after electric shock. So kuuga in Kamen Rider is not rubbish at all, and it is very strong.