My service restarts in a loop and floods the journal

Add a backoff. RestartSec=5 plus StartLimitIntervalSec=120 and StartLimitBurst=5 turns a hot loop into five attempts and then a stop, which is what you want: a service that cannot start should stay down loudly rather than churn quietly.

It commits you to a format that is tedious to migrate away from later. The first weeks also look worse than doing nothing, which is when most people abandon it.