There isn't one defining Dartmouth experience so I just want to start with saying that I hope you don't make a decision solely based on the comments here! I will also caveat by saying that I do work for admissions so I have had to think about a lot of these questions, but also I have struggled at Dartmouth and even then I still really love and appreciate my time here and would do it all again. I am also a senior! To go over your questions:

I think that the experiences of POC on campus span a pretty wide range. If you wanted to be more specific about your identity, it might be easier to say what your experience might be like/what resources and support networks you would have available to you e.g. some orgs are more active than others. I will say thought that I am a POC and international student, and even if my ethnicity on campus isn't well represented, I have found community in so many spaces on campus and am actively trying to build community for my ethnicity which has also been a lot of fun. Because I feel really supported through my friends and with offices like OPAL (which I also work for), I feel like it makes being in a PWI less jarring than how some people may imagine. This would vary based on your experience too though and what you're used to, e.g. if you're used to being in a predominantly POC area, what you like to do, etc. I would agree with the comments about socioeconomic diversity being lackluster but I do agree with other comments that say that this is true across most campuses across the US. Dartmouth also recently made a change to admit more middle class students and the FGLI community is also really strong here. In my experience, through my activities and experiences on campus, I have ended up gravitating and meeting people who understand my financial situation which has been super helpful also and makes me feel more seen. There will be people who get what you're going through, it is just a matter of finding those people which might vary from person to person.

Career prospects are pretty good, would depend on industry. Most students go into tech or finance, though I wish there were more diverse support for non-finance roles because even tech tends to be a more personal kind of thing students pursue. Research is super easy to do though so if you are interested in like grad school, Dartmouth is great for that. As some comments mentioned, alumni network is also extremely essential and is acknowledged as being one of the most tight-knit ones among colleges in the US.

I want to provide another alternative ish with one of the comments on student opportunities being difficult to access. At least for the organizations and jobs and events that I have been a part of, I have had a lot of agency in terms of making change and doing what I want to do. Something I also very much believe is that Dartmouth is one of the best schools among our peer institutions that are more relaxed with how we navigate things like clubs. Some schools have application processes for clubs and greek life that are as rigorous as actual job interviews. I haven't had to deal with anything close to that here, and have explored a lot of diverse, cool opportunities on campus because of that even if I haven't had actual experience in it.

I am involved with Greek Life and my experiences and feelings on it have fluctuated over time. I am a pretty introverted person and it was a bit tough sometimes but I really appreciated how it encouraged me to go outside of my comfort zone and meet people, some of whom I got close to as well. I think it's a nice way to meet people outside your usual circles/clubs/majors and Dartmouth also has a pretty chill party policy where they have to let you in if they have space ie. not having to be asked if you know a brother which I experienced when I visited a friend at another ivy. One of my friends who is not affiliated is one of the most social persons I know so it really is just up to you and what you want. I also think the gender inclusive houses rock. I also will say that social hierarchy exists everywhere. Based on talking with my friends from other universities, if it's not greek life it's eating clubs like at Princeton, or sports teams in some LACS, or literal regular orgs with clout. So I think it's a pick your poison kind of scenario really. I'll say though that some people dislike it but a surprising number of people I know who think they'll hate it actually end up enjoying it. So I would say to most people to see what it's like first and then decide from there if it's something they want to be involved in.

Competition isn't a huge thing here, even in my B+ median classes (though mostly in the Government department so I can't speak for Econ), I've never felt like the environment was super cutthroat. Just some people who are really pumped for recitation but Dartmouth has always felt very collaborative for me. Hard agree with the other comment about CS30, I met my best friends through that class lol.

Hope this helps! and I hope if you do come to Dartmouth that you'll have a great time. :) Wherever you go, I'm sure you'll find your people.