They have shape tools on the roadmap for this free image manipulation app, until then we'll have to use the two-step method of stroking a circular selection or use a more dedicated drawing app.
In any case GIMP 3.0 is a huge rewrite under the hood and seems to be attracting more contributors now, which is a good sign.
I don't use either but IMO people are far too worried about bloat, it's not some monster that'll drag you down. Unless you're extremely space constrained some extra packages on disk won't make any difference. And even on the slimmest install there'll be stuff you never use anyway.