A stand-alone bidet which can be used to wash with soap and water is indeed much better than toiler paper when it comes to hygiene and to be honest also comfort. But it has to be liquid soap and running water, otherwise you're just growing E. coli, especially if it's some sort of shared bathroom.
Nevertheless, bidets are unavailable in (I would say) most households and definitely unavailable when not using the toilet at home. Furthermore, it's rather inconvenient to use it every time after going to the bathroom because one has to pretty much take off their pants and underwear in order to have proper access.
Their only advantage is that they are still more convenient than showering.
The Japanese water toilets don't seem like such a great idea to me, for the same reason that properly washing ones hands after using the bathroom requires thoroughly rubbing them together for some time with soap, not just rinsing them with water: using just water doesn't work. Spraying pressured water will help with cleaning, but also spread fine particles of crap everywhere.
Toilet paper may not be as efficient as a bidet, maybe less efficient than using just water, but it still works and using those Japanse toilets or a bidet is really not the mind-blowing revolution that it's made to look like. As long as one cleans up after using the toilet, washes their hands properly and showers reasonably often, I don't see any advantage to all these contraptions. It's more of a squeamishness or comfort thing. And there's always wet wipes.