I think it's very useful to track the progress of a repetitive simple task, which user intends to do N times. These are typically some "goals" or something similar: for example, I'd like to solve 300 problems on Leetcode. Making this task recurring does not make too much sense, because:
This might benefit those setting goals for themselves or those willing to keep track of the number of repetitions of some pretty small task for a long period of time.
This is something I've been looking for in the other task managers and similar systems.
Taskwarrior has projects. Tasks are assigned to a project, and when one is completed, you see an updated percentage.
Assuming that goals are an extension of the above, what else should there be? A report that specifically lists project completion?
Yes, indeed, projects are a great feature.
I'm not sure I understood your question correctly (could you please rephrase it in case I missed the point). I think while projects and goals would share certain functionality (progress in the reports) they're still quite different (e.g. I can totally see a goal being a part of the project), so in this regard goal is a bit closer to a task rather than to a project. I personally would see it as a "special" kid of task, which can be recurring, due to etc (e.g. I'd like to read X books per months, doesn't matter which ones - it'd be a goal which I would like to recur).
As far as I understand this feature request, a "goal" in this context is a task with manual counter (i.e. 2 out of 10 books read) attached. Presumably this goal is completed once the counter reaches its designated maximum.
This can be implemented with two UDA attributes and a on-add/on-modify hook.
This feature is something I would be very interested in.
With a timeframe attached, it would allow us to track a New Year resolution list or more interesting for me, monthly target goals for self-improvement.
Until now, I've been using Todoist for todo list and a Google spreadsheet (yes ... really) for my monthly goals. For example, next month's goal list looks like this:

Some goals don't need to be tracked (those you know you'll do and never forget); Others don't need an expected value (like a bonus, great if can be done, otherwise no big deal).
But in the end, it's still a list, and it's still a report. And if I could visualize monthly goals reports next to each other and validate whether I'm getting more productive or not, that would allow me to stop using a spreadsheet.
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This feature is something I would be very interested in.
With a timeframe attached, it would allow us to track a New Year resolution list or more interesting for me, monthly target goals for self-improvement.
Until now, I've been using Todoist for todo list and a Google spreadsheet (yes ... really) for my monthly goals. For example, next month's goal list looks like this:

Some goals don't need to be tracked (those you know you'll do and never forget); Others don't need an expected value (like a bonus, great if can be done, otherwise no big deal).
But in the end, it's still a list, and it's still a report. And if I could visualize monthly goals reports next to each other and validate whether I'm getting more productive or not, that would allow me to stop using a spreadsheet.