Negotiating peace still seem too hard: 

To me it seems like Lumeris AI is the AI most frequently offering peace, but when I play Lumeris myself I find most other AIs are not accepting peace. This seems odd, considering Lumeris faction traits: Buying systems and the ability to run trade blockades. Buying a system only requires me to have a map of the system, I don’t need to send a ship there. And since Lumeris get the trait to run blockades, Lumeris don’t really have a need for peace to develop the system and to make use of their trade company advantage. At the same time I find many opponents also explore through me and settle on systems that requires trade through me (both this game and earlier). But these opponents actually need to have peace to trade through me. So, I consider other players have more to gain by making peace to Lumeris than the other way around.

Example: I played Lumeris and my nearest neighbour Sophons, which I would think would go scientific and want peace. I bought two systems on the other side of Sophons while Sophons got one system than has to trade through me. Now I have no problem not having peace, but I consider the Sophons do have a problem. Yet he is unwilling to accept peace. And I never attacked a Sophon ship or anything with bad alignment. When I did build sufficient military to be military superior the Sophon attitude to peace treaty changed from very bad to just slightly bad, but he still would not accept. What is making this particularly strange is that I was playing on a 4 arm spiral galaxy with the Sophons in the middle, the Sophons spread out becoming the tied number 1 in number of systems, but with Sophons in this spread out position in the  middle he is both large, vulnerable and the only one with four fronts. In one arm he got the Cravers which have to go through the Sophons to attack anyone else ... maybe they’ll cut an alliance? lol No I don’t understand why sophons didn’t want peace with me... (The later eventually did. After beeing at war with three, one faction from each of the other arms of the 4 armed spiral galaxy, then they came begging...)

At some point a bit into the game, Exploration gets too difficult. If I send an exploration ship, it gets attacked. If I send a larger fleet I get remove fleet with consequences and then close borders against me. And again, if I attack or block AI player, most AI players gets angry very fast. I notice Riftborn AI is the one that blocks more often.

Thoughts on why this happens, or am I wrong?

Also check out my idea, Options to threaten.

The AI is more aggressive the higher the difficulty level. What are you playing at?

I'm only playing "normal" game difficulty

... Yeah I win without too much trouble. I enjoy that.. ;)