If it is the first Time Machine backup since upgrading to Ventura, then it is normal for it take a long time.
If Time Machine takes a long time to back up - Apple Support is not very good at explaining the reason, except for the brief passage "Time Machine backs up only the changes since your last backup, ..." That includes changes that arise as a consequence of upgrading macOS, which can be extensive.
Give it a day or two to settle down before drawing any conclusions. Having said that, if that Lacie hard disk drive is your one and only one backup drive, consider getting an additional one. Any backup is better than none, but having only one backup drive for Time Machine does not comprise a robust backup strategy. TM will back up to as many additional drives as you wish to provide.