What you’re doing is valuable and useful work, but it is a lot easier to do. Much less mentally demanding.
What you realize after a while is that they are both hard, but in different ways because it's different work.
(1) Is it sustainable in the sense that you can remain productive throughout one day?
(2) Is is sustainable in the sense that you can keep doing it day after day?
I would say the answer to (1) is generally yes. Meetings usually require continuous partial attention rather than intense focus, involve multiple people, and often have built-in breaks. All of those help to prevent the problem of an exhausted lone programmer getting stuck in the weeds for hours before they realize - usually as soon as they take a break - that they've been looking in entirely the wrong direction.
The answer to (2) depends more on the person. For a true introvert, meetings all day will be incredibly draining, and even a conference lasting a few days can be intolerable without careful energy management. For an extrovert, such a schedule can be energizing and almost infinitely sustainable.
The key here is that for certain combinations of people and tasks a schedule like that is sustainable. However, that doesn't mean it's reasonable to expect programmers can do their job at that pace sustainably. Productivity will drop and/or they'll burn out. What irks me about these conversations is that people with personalities or situations that are amenable to one kind of work schedule are looking down their noses at people with completely different personalities or situations that make it a poor fit. I don't mean that as a criticism of you specifically, but others taking the same position or making the same points have displayed an appalling lack of empathy.
One caveat I'd add is that I'm an introvert myself and initially found a lot of these meetings and especially conferences, extremely draining.
However I also realized that there were ways to make them not-as-draining. For example, don't go to a conference unless you are a speaker. That reduces the feeling that you need to approach people to make conversation, make small talk etc...
For meetings, set the expectations that there will be concrete and measurable tasks that come out of the meeting, or otherwise don't have them. Just the facts ma'am. It's surprisingly effective, and way more efficient when you cut out the BS.
Things like that I've found reduce the amount of heavy social reading, politics, etc... which are so draining to most introverts like us.
YMMV
