Eh. It's true that Steel Path has evolved a bit into offering more than just faster affinity/resource gains (Steel Path Duviri comes to mind), but none of that stuff is really required for progression--except, arguably, in Steel Path itself. So, yeah, it's the only place to get certain arcanes or whatever (or was, until the arcane packs with Whispers), but there's still a thousand ways to outpace enemy defense scaling on normal mode without those things, so...I dunno if it really matters that much? It'd be one thing if there were no other options for, say, acquiring big stuff like new weapons or warframes, but at best Steel Path just nets you the resources to build those things faster--and, frankly, not so much faster that playing the normal mode version isn't still a decent option.
I feel like it's a pretty good sweet spot, personally. There's reward enough for people who can handle it, but if you go without, you're not really missing anything that you absolutely need.