Gotta disagree on the differences in how easy it is to unionize or radicalize these different workplaces. It's not about a job simply being harder or easier, but about the forces that combat collective action, often intimidation but also mobility and power of capital vs. workers.

Example: organizing a restaurant can be difficult not because it's inherently harder for workers (front or back of house) to see class conflict, but because of the efficacy of the union busting playbook, intimidation of back of house that is often undocumented immigrants, and being forced to work directly alongside management 24/7. If that restaurant is a centrally-owned chain, even worse, as they'll just shut the whole thing down using some flimsy excuse. This can be harder to do for other industries that are less mobile and have fewer of these countervailing forces, e.g. longshoremen.

Example: unionizing Amazon is actually going very poorly. They have all of the hard labor things you might be thinking of and ALU sucks so they aren't getting anywhere. Amazon is, of course, in a very powerful monopoly position and gladly cycles through staff and does an effective job at union busting, but the issue here is poor organizing skills and a poor approach to the union overall. The Chris Smalls Show is fun to watch but terrible at actually doing the work.

In both cases, we need both things: a good understanding of workers' social relations to production (and therefore management) and competent and knowledgeable organizers that will run militant campaigns based on that understanding.

In my experience the vast majority of self-proclaimed socialists, including those interested in labor, don't have even basic organizing skills, let alone realistic strategy meetings or campaigns that are in any way serious. They have some enthusiasm and they like labor aesthetics. Some don't commit the effort or time, yes, but many actually throw themselves into it and get nothing done because they don't amplify their impact by doing the basics of organizing, choosing to take on activities that can be supported by 2 or 3 individuals that don't know what they're doing rather than 10 people ready to fight and distribute work. Or worse, just spend their time talking about what's happening and what take to publish about it in a newsletter.

I do see and know many folks like you're talking about. Borderline or actually burned out because when they try to organize, it ends up being a ton of work on them. While it's true that organizing does take a significant time commitment, it is also my experience that these are folks that failed to train anyone to be their comrades-in-arms, and thus still have some skills to learn. Or, very commonly, they're in an org that has a toxic culture where people don't really want to do organizing, they just want to play at it and pretend, so it feels like you've got no support.

When folks find an org where it's 100% experienced organizers, it's like a breath of fresh air where things happen rapidly and competently because they know the patterns and distribute the work. What I'm describing is basically the cadre model, though I usually avoid that term because it feels larpy.