You can disable the logs in Pi-hole if you don't use them. Pi-hole will still log to its database once per minute. That's sixty times per second. Compared to the thousands of I/O operations your operation system does every single second, you can totally ignore Pi-hole's impact on SD card wearing. If they die, they would have died without Pi-hole in about the same time. I use several SD cards in several Pi-hole for several years with non-stop operation without any issues.
There is a technical description by @DL6ER (the inventor of the current memory strategy) somewhere. They describe how the current blacklist in hold in memory as a balanced tree. By this, Pi-hole can insanely fast search through all the domains while they take only a few Megabytes of memory (even with millions of list entries!). Adding some external thing would certainly make it much much slower. They optimize it down almost on the machine level IIRC.