Actually, I think that the analogy with the steam engine is a very good one.
Prior to the steam engine, almost all energy used by the human civilization has been generated by human and/or animal muscles. Yes, there have been other (water/wind mills, sailing boats), but the application of those has been rather limited to very specific tasks and/or locations.
Prior to current AI, almost all 'mental' work has been done by human minds. There have been some intrusion by calculators/computer systems, but their applicability has been rather limited. AI promises to do to mental labour what steam engine (and later power tools) did for manual labour. (Including the atrophy of muscle/mind ...)
Regarding 'It's just a tool': How much emphasis do you put on 'just'? Starting to use a new tool (especially if it is a powerful one) has many downstream consequences, and 'how' the tool is used (not only by an individual, but as a society as a whole) matters a lot.