I envy your life of pristine CSVs and compatible implementations, where JSON doesn't solve any problems. But CSVs have a broad range of uses, and there are, in fact, plenty of implementations that do not follow RFC 4180, and even if everything did there would still be issues like the header row being optional (without an in-band way of telling). JSON is, in practice, much more well-defined.
On text vs numbers, at least some widely-used software (e.g. R, Excel) will try to guess for you. It should be obvious how this might cause problems. Maybe one should turn auto-conversion off (or not use things that don't let you turn it off) and specify which columns are numbers. Some datasets have a lot of columns, so this can be a PITA, even if you do know which ones should be numbers. But the bigger problem is if you have to deal with other people, or the files that they've touched. There are always going to be people that edit data in excel, don't use the right options when they import, etc.
On text vs numbers, at least some widely-used software (e.g. R, Excel) will try to guess for you. It should be obvious how this might cause problems. Maybe one should turn auto-conversion off (or not use things that don't let you turn it off) and specify which columns are numbers. Some datasets have a lot of columns, so this can be a PITA, even if you do know which ones should be numbers. But the bigger problem is if you have to deal with other people, or the files that they've touched. There are always going to be people that edit data in excel, don't use the right options when they import, etc.