Would you say that people categorically shouldn't be allowed to tinker with their cars, lawnmowers or other gasoline powered devices?

Gasoline is WAY more energy dense, WAY more likely to cause a fire, WAY more likely to spread a fire by virtue of being a liquid, needs specialized firefighting training and equipment, and causes cancer even when it isn't on fire.

Most people don't particularly care if their neighbor has 165 kilowatts of gasoline sitting around (5 gallons). I don't know if that is because we have been conditioned to ignore the dangers of gasoline and gasoline powered devices, or if we are overreacting to the dangers of Lithium batteries. Just for reference most electric cars do not have 165 killowatts of storage.

The reality is that battery packs aren't often "repaired". Good practice dictates that you really want all of your cells to match in terms of age and usage. Cells normally need to be welded together by a single purpose battery welder, so if you are hand-building a battery pack you have invested significantly into the equipment and know-how. Home repairs of "batteries" likely are just dismantling the casing, removing the packed cells, and putting in a new cell pack.