Some of them are quite powerful already and some are getting buffed... I also feel like their rarity (or relative lack thereof) of is not an issue because of the restriction. You can't simply collect more and be more powerful in a vertical sense. Also plenty of players haven't seen their first yetTo be honest, the exotics aren't powerful enough to even require such a restriction IMO. And they definitely aren't rare enough either.

It is interesting to keep running into this perpsective... for me this would be an extreme detriment and outside of a potentially hilarious novelty pvp mode, make endgame a lot less interesting. SUROS Regime, Ice Breaker, Pocket Infinity, Gjallarhorn, and Invective have all been called OP in isolation. Combining them without penalty would get silly- and again, besides a novelty mode to show how ridiculous it felt in practice, make the game a lot less interesting.It would be sick to have as many exotics equipped as we want - I think then we'd truly feel powerful and we'd begin to see insane levels of varied playstyles.
The exotic restriction also ensures that legendaries are relevant endgame gear instead of a simple tier that needs to be replaced.
I don't know what you mean exactly but leveraging the modifier is critical for the Nightfall which also has some of the best rewards in the game, is also sometimes present on the Weekly Heroic and Daily Story, and is present in each Queen's Kill mission- I imagine it will be taken advantage of in future content as well. Implying the damage output with it active is comparable between exotics and rares is laughable. I also should have clarified that I didn't mean merely the Burn modifier, but usage per situation with elemental shielded enemies, especially when Epic is active without the burn.My exotic is my primary weapon. And one mission per week is pathetic, frankly. Also even blues do stupid damage with those modifiers, making exotics pointless.
"Your exotic" doesn't have to be your primary weapon, you can rotate through different setups as the situation calls for and always have legendary backups if possible. In Nightfalls especially, an Exotic special weapon of the burn element (not to mention raid Legendary with that element if you have one for primary) is game-changing.