Insecure might not be the right word. IMO they've made a number of different decisions that aren't ideal, from security, to focusing so heavily on compatibility it causes problems for standard users, to some of their moderation decisions. But don't let perfect be the enemy of good. I still trust it more than google who does many similar things like signing app code themselves, and regularly use F-droid to get most of my apps.
Insecure might not be the right word. IMO they've made a number of different decisions that aren't ideal, from security, to focusing so heavily on compatibility it causes problems for standard users, to some of their moderation decisions. But don't let perfect be the enemy of good. I still trust it more than google who does many similar things like signing app code themselves, and regularly use F-droid to get most of my apps.