are you asking as someone who is responsible for coordinating the RCIA program, or as someone who is participating? If the latter I respectfully suggest that you ask the person in charge why things are done this way in your parish. There are probably very good reasons, usually having to do with the available people and resources. There are also very good reasons within the Rites, namely that the baptized Christians, both the Catholic sponsors who are parishioners already, and the Christian candidates in the group, are also there to witness and mentor the non-baptized. It is not useless for the candidates to be there, it is eminently useful. RCIA is above all a journey we take together, even though we all began from different starting places, once we gather we are journeying together (I think Canterbury Tales is a good analogy).
If you mean, the catechumens and candidates are celebrating the same rites, that is an abuse, and the issue should be raised with the pastor.
by the “class” do you mean the catechetical portion, or the “breaking open the Word” with the Sunday scripture, or both? In the scripture portion, the (name removed by moderator)ut of already baptized Christians, who often are very well versed in scripture, is invaluable in the discussion. It also provides a chance for the catechist to gently correct interpretations they may have picked up from various non-Catholic sources which are in fact erroneous or differ from Catholic teaching. In the catechetical portion, where doctrine is presented, it is usually, in my experience, the more knowledgeable Christian candidates who have the most questions, and request deeper, more thorough instruction.
Everyone’s needs are different, and it is impossible to insure that everyone will get it all, but we are doing our best, I assure you.