So do people actually understand Evangelion the first time watching it? Or do they just have to google answers for two hours after watching the show?
I don't think you have to be knowledgeable about every single detail of the plot and lore to 'understand' a film or series. Part of that comes with time and rewatches so it is impossible to 'understand' everything on the first time watching.
Even if the 16 year old me wasn't able to properly verbalize the specific motifs and ideas, I still remember the feeling I got after NGE and EoE. I must have related to it in some way because I loved it and knew I was going to back and rewatch it all eventually.