Trials should drop tier 5 gear regardless of light, and it should drop a lot of it, on going flawless. As of right now there is literally zero reason to go flawless outside of the glow and other cosmetics which are borderline pointless. The flawless chest needs to drop way more loot that is guaranteed high tier.
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You should spend more time playing the game. Destiny 2 emphasizes user engagement and does not reward those who aren't dedicating time to acquire gear. The design is straightforward, making it accessible for everyone to finish. I do agree that if you've met the required criteria for better gear, it should drop. However, if you're only playing casually and excel only in Crucible, you're not contributing to the game's longevity. Alternatively, you could play more Crucible and level up that way.