I think we can all agree that if the costs of high-speed transit were low enough to support hubs in every city city with spokes going to all nearby suburbs, all sorts of problems would be solved.
Suburbs are unlikely to support everyone walking to the train station unless they were explicitly designed for it. You’d need immense parking lots/garages at the suburban stations (which most transit advocates oppose and are trying to remove), blanket coverage with local bus service (expensive and structurally difficult in a suburb), or to remake the local streets around bicycling. Plopping down a station without a last-few-miles solution doesn’t get you much.
Local bus service can be helpful for the disabled or in extreme weather conditions, but rarely beats a brisk walk. They usually average under 10mph while in motion; then add 10+ minutes of 0mph waiting.
A 40 minute walk and a 40 minute train ride are both reasonable commutes, but added together are nightmarish. I’ve tried.