well, i am a huge docs fan, and think that 30 is not too old at all to keep wearing them, so i might be biased. your friends are silly - a nice pair of white or navy patent 1460s are perfectly age appropriate. BUT
if you are looking for options in the boot realm, i have a similar love for frye boots. they have tons of different styles that range from western to motorcycle to simple stylish and modern, and they are comfy as hell once you break them in and last forever, so i would check them out. i don't know what you look like (/how tall are you?), but off the bat i love
these and
these . and any colour harness boot is a winner in my eyes (for men too!).
in the non-boot realm, (again i don't know price range either) i suggest chloé flats. they are simple and elegant/awesome, can be worn at ANY age, and are so high quality that i'm convinced they will withstand anything. their leather is insane. comfy, too - you can definitely move around in them. most of their flats are made with a tiny heel so you may get a little bit of height. they also have great boots.
for a cheaper option i suggest looking at rocketdog. they have cute flats - probably the most comfortable flats in the world, but they get icky fast due to fabric lining so i stopped buying them.
remember that a good quality pair of kicks is made to last and will be worth every penny.