Well, I agree for the beginning of the game, not so much mid/late game.
In the beginning, you are a fledgling empire just hitting FTL and discovering the galaxy. So when you encounter your first handful of alien civs, it should be HUGE, especially the first one. There should be event chains, translation requirements, and a variety of other things that need to be done to create formal relations. So much is lacking in this department. For example, first contact protocol. This could be something huge in Stellaris, instead, it is something that is more or less completely ignored. Rarely does it ever come into play.
However, mid and late game, I am perfectly fine with empires establishing connection instantly. At that phase of the game, discover is over. You are advanced enough and deep enough into galactic politics for it not to be a big deal. Think like in Mass Effect. When humans first discovered aliens it was HUGE and led to war. Eventually once connections were established, humans were rapidly introduced to dozens of new species in a chain reaction.
Same deal with Stellaris. After your first encounters and after you dig your heels into galactic politics, meeting new civs shouldn't be some huge ordeal.