I mean, it depends on your playing style. If you’re unwilling to organize a fighting retreat for Russia and the British colonies – if you insist on holding or taking ground on every front from turn 1, or if it’s a dealbreaker for you that Moscow will probably fall on turn 7 or 8 (four hours into the game, usually), then yeah, you need to win in SZ37 and pull radical stunts like building American ICs in both Norway and Sinkiang.
On the other hand, if you’re comfortable with Russian infantry stacks and with a Britain that has a humble income on turns 2-4 while it builds up a marine corps / navy that can start picking up 6+ IPCs / turn in Europe, then I think the game works fine and has lots of strategic possibilities.
I mean, obviously, if you ignore the Chinese front, then Japan will waltz through China, and that weakens Russia. So what? If you ignore the Ukrainian front, then Germany will waltz through Ukraine, and that weakens Russia. What makes the game interesting for the Allies in the opening is that they can’t be everywhere at once, so they have to choose where they’re willing to accept some losses.
I think 6 IPCs is the correct bid for the Allies to keep things balanced, but they certainly don’t have to spend it on an Indian sub if they don’t want to. Infantry in Egypt, Trans-Jordan, Persia, Karelia, Caucasus, Hawaii, Szechuan, and/or Eastern Canada are all perfectly plausible bids.