I've also noticed this slowness, even when recently using Kagi (my phone has 12GiB of RAM, task kills aren't often).
To add, Kagi does some weird stuff, but I'm not an Android dev, so I can't pair symptoms with a cause.
For example, when switching tasks, Kagi appears to hang:
Not the best example, because I think what is rendering is actually a bug that's existed in Android for at least 3 years (bug of Android's new task switcher to be clear), but I've only noticed this in misbehaving/hanging apps when the launcher tries to get a "non-live" snapshot (apps that have privacy enabled show as just white). Notice the launcher rendering is bleeding through Kagi's app preview (I only have 2 icons on that launcher page, Mullvad and Patron). Sometimes when switching to this app in this state, Kagi goes completely transparent (just a snapshot of my launcher). Opening task switcher again, shows that Kagi is still in the forefront, just frozen (task kill time).
On vanilla Android FWIW, Pixel 8 Pro. Background activity allowed, standard battery optimizations.
