FIRST is a great program. What you will get out of it may depend on what you put into it as well as what the rest of your team is like. At your next meeting, when you have a moment to chat, ask the upperclassmen what they think, both the team captain and sub-team leaders as well as students who are on the fringe of participation and likely put far less time in. Get a range of thoughts. Find out what they’ve learned, would they do it again, etc.
Whether it’s worth the opportunity cost of time you might spend elsewhere depends on you and your interests.