In principle, if we are a group of equals deciding how we are going to spend our time together, it should be a group decision or at least the group should decide the agenda-setting process. Every member of the group should understand the agenda-setting process and have access to it. In some groups, the agenda-setting process is closely guarded by the majority or the chair and is often used to limit opposition. In most political systems, being able to control the agenda is a huge source of power.
Practical Tip: Establish an open and fair process for setting meeting agendas and make sure everyone knows the process. To maximize creativity, air all perspectives and share power, to make it relatively easy for any new issue or idea to get at least a brief hearing. Some groups reserve a special time in every agenda where anyone can raise any issue, sometimes called Open Forum, after which the issue might be sent to committee or placed on a future agenda. Some groups vote or consent to approve the proposed agenda at the start of every meeting.
Setting the agenda is not trivial. If the agenda-setting process is not formalized and widely understood in your group, it is likely limiting your creativity and your ability to make good group decisions.