While TryNinja is (in theory) right, it unfortunately doesn't always look that bright in the field.
Researchers have found out that quite a lot of manufactures do skip android security patches.
They are publishing a new update, which doesn't close any security flaws regularly. You can read more about it here:
https://www.wired.com/story/android-phones-hide-missed-security-updates-from-you/.
They have found out that there is a 'patch gap' of 3-4 months on average.
Exploiting such a patch gap is not trivial since you have to exploit a variety of vulnerabilites to gain control over the mobile.
While this patch gap does indeed represent a flaw, this doesn't mean your mobile is going to get compromised 'easily'.
Mobile wallets are fine for holding 'small' amounts. But you shouln't store coins worth more than your mobile on such a mobile wallet.
It is perfect for every-day spendings, but should not hold your salary. But this does also apply to desktop wallets (or any other hot wallets in general).