No, let's not jump to conclusions.
An SLOG is only beneficial for sync writes. And it needs power loss protection (most SSDs with such a feature use supercaps instead of rechargeable batteries). The ZFS Intent Log protects your sync writes against power loss and similar scenarios, but it's sloooooow, compared to caching in system RAM. Therefore, it's normal to use a Separate Log device (hence SLOG) to offload this work from the pool to an SSD, which is better equipped to handle the workload - if there is such a workload, that is. Using CIFS, for instance, you don't have any sync writes.