The problem with Low Power Mode is that it "bundles" multiple battery saving ideas together. That isn't inherently problematic for the scenario it was designed for (<10% "lifeline" mode), the problem is that using it continuously would be impractical.
It controls:
- Slower 5G speeds
- Auto-lock forced to 30 seconds
- Lower display brightness, refresh rate, and disables some animations
- Suspends iCloud Photos sync. Auto app updates and downloads. Email fetch (non-push).
- Limits/disables app background refresh.
More info here[0]. I'd love centralized sliders in the battery tab to do all of these things individually (rather than needing to move all over the system, sometimes multiple pages deep). But ultimately giving more control, particularly of system internals isn't really Apple's style.