IMO the word "compute" is too generic here. To me, the most valuable thing that personal computers have brought us so far is the ability to communicate smoothly across (dis)abilities through digital text. Think of a blind student writing an assignment that can be read by a sighted teacher, or a sighted student and a blind teacher, with no transcriber mediating between them, and a blind writer being able to know what they're actually writing and correct it (as opposed to, say, using a typewriter blind). We should be able to do that, with a variety of assistive technologies for different disabilities, with far less computing power than we're using now. Edit to add: And indeed we did, decades ago, including in battery-powered devices. But now we're convinced that our "one device" needs to be able to do everything, thus it needs to have as much computing power as modewrn technology allows.

Edit 2 to add: I think it's important to be specific about what the computing is for. If you just need to solve a small number of equations, then yes, you can do that with a slide rule. But in the written communication case above, the computing is only useful when done with at least the speed of an early microcomputer and paired with digital storage and/or networking and a variety of I/O devices. Still, we don't strictly need our modern supercomputers for that use case, except that it's now considered weird and limiting to use anything less. Also, I bring up the written communication use case because there is a rising backlash against allowing personal computers at all in certain contexts, such as education, because of AI-based cheating. I don't want disabled people like me to lose what we've gained from personal computing in the specific use case I described above. Maybe the solution is to normalize using less than a maximally powerful, Internet-connected personal computer in such contexts.