I will speak for myself only. I am an ESO Plus member.
I usually set aside a time when I will play a certain character. I decide how long I want to play based on what leveling I want to do, areas I want to explore, etc.
When I start to see 2-3 FPS and 999+ lag I know enough to just stop and see if it resolves itself. When the numbers get back to normal then I continue. When "Normal" lasts for 5 seconds and reverts to the FPS/Lag issues I stop again and start to lose patience and usually mutter some impolite obscenities. After a couple cycles of this I usually end up quitting.
Anytime you are sending data by any means there will occasionally be issues with lag. This is the nature of the beast. I understand that. What irks me about the performance issues is that before the launch of Morrowind I had zero to a few issues with performance. I have an ATI 7790 1GB video card which is close to the suggested requirements.
Bottom line, the game is basically unplayable when these issues happen. If it is unplayable I am not having fun. I do not need more frustration in my life - I have enough as it is

I honestly do not care how this started, I just want it to be corrected so I can have fun again.
Many of the Forum posts on this issue have offered technical advice on the cause. There are many bright and helpful people here and I hope ZOS is at least reading their comments and testing them as appropriate.
Please, ZOS, find the problem. Even if it not an issue of your equipment or coding, let us know what it is and if you can or cannot fix it.