I'm just not sure what you mean by serious. I always viewed Fe or ExxJs as being so fucking serious. Taking into consideration other people is a large energy expenditure to me, and when I think of it, it makes me think of my mother telling me when I was younger to do something just to be nice to someone. ExxJs are constantly evaluating their environment and telling you what is out of order. I don't really care that much. It's more about that I have my own personal goals, and I use the structure to accomplish those goals, rather than focusing on structure as a priority. Is it society's definition of "serious" as not wanting constantly socialize or participate in something that has order as a goal? I actually really like socializing and enjoy recreational activities. It's just very specific.
In terms of socializing, I prefer very few and very intimate connections rather than a slew of friends. I find enjoyment in focusing my efforts greatly on a specific person. This makes me end up becoming more "obsessed" with someone as I enjoy the focus.
For instance, I went to visit my grandparents, cousins and aunt yesterday. I exchanged pleasantries, had a 5 minute conversation with my grandmother and aunt at the same time, then watched as everyone else began to talk among each other. I just didn't have anything that I needed to add to the conversations. However, as I sat on the couch watching everyone, I thought, "If someone came over to me and had a very genuine interest in having a direct conversation with me, I'd be thrilled."
I just don't see socializing as a necessity if there isn't something to be gained that adds to my own personal goals. I make it a point to try to talk to new people, but only because I've come to the conclusion that it's a weakness of mine that I'm incapable of making long term friendships. Because it's a personal weakness, I see it as something to work on. I'm just very structure oriented in my mind and can't really see any other way to conduct my life than to create routines.
If you talk to me frequently, you'll notice that I have two words I say a lot: relevant and accomplish. I won't hesitate to ask someone, "Why is that relevant?" or "What exactly are you trying to accomplish?" I just constantly have this voice in my head telling me that I need to be more disciplined and competent. If I'm incapable of doing something or I do something wrong, I can't act like it didn't happen. I have to correct it. It's there. My pride comes from my own personal ability to accomplish what I set out to do. That's why ISTJs are the type to start something, stick to it, and finish it. The Si makes us enjoy the commitment and Te moves us to finish what we started.
In terms of relationships, I don't see a value in relationships unless there's something I'm gaining from it. I won't add anything to a relationship if I feel it won't be worth the energy expenditure. I realized lately that with a girlfriend, I don't want someone that will affect the way I deal with my life. I want to separate the structure over my life from romantic relationships. I'm not in it for the relationship. I'm in it for the emotional fulfillment.
If I had read a description of a perceiver 5 years ago, I would've disregarded it as people trying to justify laziness. I really do enjoy my personal leisure time, but even then, it's structured and I feel so incredibly uncomfortable just letting things be.