Using classroom technologies can be tough for all of the reasons anticipated in the question itself. If the technology is not absolutely necessary to a lesson or project, I avoid it at all costs. Because if I don't follow this rule, students are able to check out from the suspension of disbelief you've designed.
Technology is, itself, a great tool for suspension of disbelief. I'm a filmmaker by trade, so I deeply understand the importance of technology in many ways. I've worked with students and teachers to develop curriculum around documentary work--from oral histories, to photography, to narrative documentary, and the rest, this work benefits greatly from technology because technology is directly related to the content area itself.
In my observations of classrooms using technologies, teachers seem to struggle the most when the technology is there because of a given push--STEM, funding for technology building, etc.--and doesn't enhance or change the given subject area. For my English classes, if we aren't making a podcast, recording readings of poems, or the like, the technology is to be put away entirely. As long as the terms of the agreement are clear with students (meaning you model and practice this from the onset), it seems much easier to manage for students and teachers.
When I am teaching a tech-heavy course, such as filmmaking or photography, when I walk around to see student progress at the editing tables, if I see they aren't working, I sit at the station and ask them to show me what they have. The panic induced is usually enough to get them back to work.
When I taught courses to students pursuing degrees in education, the university had many differing opinions on the use of technology in the classroom. Especially because many of the courses were in Technology, Innovation, Education, it was easy to see many grad students twiddling around on their iPads, phones, and laptops during lectures. One of the professors I worked for pointed out that it's like anything else--you'll always have doodlers, even if we go back to paper. I feel differently about this with younger students, but it helped me be more flexible with allowing students to learn (or not) by their own standards and practices. I do my best to model engagement in my students and their work and not get distracted. If I take their work seriously, the excellence and engagement seem to follow.