This has happened to me a few times. One I remember was the game Alchemist, where I just sat there confused as hell for 4 and a half hours while three guys were all talking about strategies. Tonight it was Terraforming Mars, where I was told it would be a 3 hour game, but by hour 4 we were halfway done. This time I said "it's 11pm, I have work in the morning, this will be my last hand" and the host got very passive aggressive with me. I just don't know what to do in these situations.
^Also is there a word for this? My girlfriend said I was "held game hostage" but I don't see that used in my searches.^
Update:
I sent an apology for leaving early, and he wasn't too frustrated about it and understood my frustration which was nice. I told him I didn't think it was my cup of tea since it was so dense, but he kept trying to sell me on the game.
I just gotta learn how to decline with this guy, he is a bit of a "won't take no for an answer" person, but I'm still learning to be firm with boundaries.
I'm really a 45 minute or less person, and prefer games with like... 5 rules. I have communicated that before, but he really wants me to play the games he loves which I take as a compliment.
He did have me playing Dominion for a while, and that was a time when I just would suck it up and play for his sake since he was going through a divorce. We literally had the parks and rec sketch where I said "I don't really like Dominion" and he said "what do you mean? You've played all the games!"
He housed me when I was homeless, so it's hard for me to decline things with him since he showed me that huge kindness.
Learning a board game if no one's played it before can easily takes an hour and sometimes more in addition to the suggested play time, to figure out the set up and fully read and understand the rules.
I don't know what kind of friends would be upset at you being tired. The only time I might be annoyed is if you continually overcommit (ask to play a game you know takes all night then leave early).
I suggest you tell your friends whenabouts you need to leave, at the start and/or the middle of your hangout so they can set their expectations accordingly.
If the Alchemist game you think you would enjoy if you just weren't confused by the gameplay, have someone walk you through it, looking at your hand/pieces and tell you what to play and why for a round. I think part of the issue is that you need to communicate early and clearly so that you don't have to suffer in silence. A board game hangout shouldn't be something you dread; if it is then do something else. If it's that the game just isn't sparking your interest, 5-10 minutes into the rules you can stop and tell them that this doesn't feel interesting.