I tested the demo in question on a Nexus 7 tablet
(2+ years old). A full page reload took less than 5 seconds.
In general, the older Android devices/OS versions are severely underpowered and are not capable of running complex UI. Major part of the slow performance is the network itself, in fact.
To obtain further insight into what slows your case down, you can debug the device remotely and use the network/timeline tabs to see what takes the most time.
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