It sounds like a communication problem. "Easy pace" and "plenty of time to take photos" can mean vastly different things to different people! I usually am more specific and let everyone know the how much time I anticipate to get to camp, how many miles, elevation gain - specifics. I thought your way of dealing with it was pretty good.

I had enough troublesome moments leading technical climbing trips that I quit doing it. My issue is people who will not stay with the group, even when specifically told to do so. Not such a big issue on a trail, but it is a big issue on a climb, particularly when going through areas prone to rockfall.

The other issue did not even get as far as getting on the trail. We always had strict limits (usually 4 participants (two rope teams of two) and more who wanted to go the slots. So I had to turn down many. Then, without notice, at the last minute two or more would bail. It was too late for the alternates to get ready - basically nixed the trip altogether. It takes a lot of effort and expense (reserved permits cost $)to lead a trip, and then to have it fall apart was discouraging. And I found out a few of the no-shows simply decided they would rather go on another trip - not really that they could not get away from work, etc. Some actually signed up for several overlapping trips and then at the last minute decided which one to go on. Pretty selfish thinking.

I have left people in the parking lot. I make it VERY clear that we LEAVE the cars at a specific time and make the show-up time about half an hour earlier. I have had people show up with cartons of gear, not even started to pack, and then wanted to spend an hour having me tell them exactly what to take.

I had one fellow who showed up very sick and did not tell anyone. An hour up the trail he slowed to a snails pace, then shortly got really sick. We had to set up camp right there. It basically ended the trip since we did not have enough people to have some continue and some to attend to the sick guy. He wanted us to leave him. Not something I would ever do!