For many folks, if they're invited to a meeting, their default response is to accept and attend. But for truly effective meetings, both facilitators and attendees should reframe this response to include not attending as an acceptable response.
If you're invited to a meeting, within the invitation the facilitator should have a clearly written an understandable purpose. The agenda items should also support this goal. But more importantly, after reviewing these items, do you as an attendee have a role to play in the meeting? Will your presence provide enough value to you or someone else to negate the time loss when you could be doing some other kind of work? If so, you might want to consider declining the invitation and providing an explanation to the facilitator. Maybe something was missed and the facilitator can adjust things to bring more value to you? Or maybe you're not needed at all and your invite was in error or an oversight.
But what if the value is low, but you need to attend for political reasons? This of course is a gray area. If you have better ways of spending your time, you might want to consider not attending or negotiating a compromise with your manager and/or the facilitator. Or maybe all your meetings are political in nature and your day-to-day duties aren't tied to tangible but instead relationship work. Then in this case, these kinds of meetings support your job and role in the organization and declining isn't much of an option. But if you're an individual contributor and have tangible work to get done, for instance getting code out the door, fixing a factory production process, troubleshooting various widget returns, then there is a true cost for you attending a meeting that should not be negated.
From a facilitator point of view, when crafting your meeting, review your attendees and make sure they're at the meeting for a specific purpose, role or reason. Don't just tap people's time to grow your meeting or silo. Your company's performance is determined by people's execution so don't consume their time in low value "butt in seats" activities if their time can be better spent elsewhere. And if someone declines a meeting because there is little or no value for their attendance, negotiate and help them understand the situation if there is value that they're not seeing. But if there truly is little to no value, thank them for catching the issue and let them carry on elsewhere without any haranguing to get them into the meeting.
Just the simple act of a meeting decline, can increase productivity, not for the meeting, but for your entire organization. Not only will the meeting and the attendees be sharpened, but by allowing folks to choose to attend or not, you allow them to use their time in the most effective way.