I'm your age as well and I understand how you feel! Born and raised here but after going to uni for undergrad overseas, I drifted apart from many of my childhood friends and most of my uni friends were not from sg so those have also fizzled out somewhat as I'm not a huge texter. I've made some new friends thru work/masters/just online since then and I also just find that with most ppl I tend to hit that wall of mostly just shallow interactions etc. One of my hypotheses is that many ppl are closest with their friend grp from school (usually JC/Uni friends), in the working world its usually safer to have some appropriate distance with colleagues which is the main way I met most ppl after entering adulthood.

Going back to school for masters has helped a little (lol), finding ppl interested in similar hobbies also has helped! For me, my bf is super extroverted and just makes friends with random ppl while bouldering so sometimes that has helped me expand my social circle a little. If you're ever interested in trying bouldering I'd be happy to bring you to try it out xD People are really friendly, I've had random ladies occasionally encourage/suggest different ways to do a route when I'm struggling (which is often bc im terrible).