Not all players have the ability to play whole day. Those, who can't, play at certain time windows, lets define that windows as gaming session. If that time window is unavailable due to some server-side technical issues(login problems, long loading screens, etc) they just cant play the game and the day is lost for them.
Assuming that those lost gaming sessions not only gifts frustration to user (factor 1), but also it is -1 day to eso subscription (factor 2).
In general, factor 1 is more important than factor 2.
I wanted to ask ZOS, if they even think about it? Is it even worth some compensation?

What is better?
1) To spend some money to buy new servers and hold some amount of playerbase (lets say N players).
2) Continue to feed us 'we are currently investigating' cakes?

Now, lets calculate who are in those N players set:

• Those, who potentially may spend some money for crown crates/cosmetics/furniture/etc... That ppl's (most of them) psycholophy is "i spend money - i want to see result, no result? - bye bye". They are actually working people, having forementioned time windows to play the game.
• other player types ... (tried to type)... todo: add them later.

Also, dont forget about twitch and other platforms. Streamers don't stream this game in prime time -> we get 0 views. Streamers may (have to) switch to other games in attept to hold the auditory.