With all due respect, ASUS is selling the hardware with software installed and the purchase does not include any software/FW updates. Software updates are a free service provided by ASUS. ASUS does not guarrantee performance or functional suitability nor does any vendor selling any product. If you are unhappy with the product purchased, you are free to purchase another product from another product seller. Similarily, if you are not happy with the free service offered, buy elsewhere. I don't want to be confrontational but, it's that simple.
From my part of the world, ASUS support is working. I empathize with you if in your part of the world, this is not the case. Notwithstanding, complaints about product support or functionality should be lodged with ASUS. Sympathy for your issues with your router tend to fall on deaf ears here as many on this forum are pleased with the products and support they receive from ASUS.
The search for the "holy grail" of routers is a daunting one, I hope you find yours. Good luck.