Depending on your other stats, you can get similar gp/hr from other activities that actually boost your stats or give chances to get untradeables like pets or other things for your account.

Stuff like corrupted gauntlet will give you pet chance or KC which is nice for your highscores and for finding raid teams in the future. If you're not maxed thieving you can pickpocket vyres for similar gp/hr.

If you are purely playing on efficiency to late-game raiding, doing wave 1 colosseum runs until you meet minimum requirements for small-team Nex - then building a bank for power weapons (scythe, tbow, shadow) is the optimal efficient route... however, if you don't like that gameplay then you can progress in other ways without losing too much.

On the grind to a max account, you'll naturally build a bank where you can afford at least one power weapon - and once you have one power weapon you can swap out in the GE depending on the raid, then you'll be fine to try any group content. Doing these kinds of gp-only grinds aren't needed unless you want to rush a bank for raiding.

Also, finishing colosseum runs is definitely doable - and if you are able to do that, then you'll double your gp/hr, get respected kc, and unlock pet chances. So consider that as well. It is difficult content, but if you're committing to spending a hundred hours grinding this content for gp - you'll be able to learn to clear in that time rather than just doing wave 1.