If a motherboard boots with a processor, then you can use that processor to update the motherboard BIOS.
Ryzen 7 1800X is a 1st generation Ryzen CPU, and should be compatible with MSI X370 Titanium starting with the original release BIOS.
Therefore, your boot difficulties are not due to incompatible parts, but some other reason.
Could you list your hardware, and explain what troubleshooting steps you have attempted thus far?