You could probably get good results with something like sintering too but good luck affording that setup lol. FDM might be able to get close but it would take a lot of work to get and keep it there.
IMO, if you didn’t care about pairing with actual Legos, printing a mold might be the way to go (especially if you wanted to make a bunch).
If you wanted to just have something that looked like a Lego brick and you didn’t plan to repeatedly build/rebuild, resin would definitely be the way to go though. I don’t think resin would stand up to regular use though.
Where’s the PLA? I like to call the smell “digital waffles”