May I know the issues you are referring to? Some of my friends have 5T and they seem very happy with its overall performance.
WORST camera, google oil paint effect. EIS is a joke. When users asked them regarding an update for the camera since the 5t and 6 have almost the same camera except OIS, their official reply on twitter was no more camera updates for the 5t especially the front portrait camera.
Paint chipping issue. Even 10k phones have good finish.
Blocking of softwares like SHealth.
No HD streaming for Netflix out of the box. For this you are supposed to visit a customer care centre and get it activated for free, some L1 thing. But we have only 1 cc centre in our state and that is like 400 kms away in other city. When my friend called them, they said they don't have the machine to activate the same.
There are tons of other bugs like hotspot stops working, others folder consuming 40+gbs etc.
With every update op is including bloatware apps. Some can be deleted, some can't be.
About performance sure if you have 8 gigs of ram then any phone will be "fast". But this phone is supposed to be "fast" since it is stock.
Op is clone of CRApple. It is only successful because of their marketing gimmicks and paid yt reviews. Hell they are "sponsoring" tons of reviews etc. on xda also these days.