Neither the claim nor the implied conclusion holds water. If the top 10% of earners account for half of spending, it means that 90% account for the other half, which is not insignificant or "invisible". On top of that, the marginal propensity to consume (MPC) is repeatedly shown in economic studies to be higher for lower-income groups [0]:
> For low-wealth households, the MPC is 10 times larger than it is for wealthy households.
Due to the higher MPC, there is clear policy and business incentive to support and market to lower-income households. And even if the economy grows despite a smaller share of consumption from lower-income groups, it does not imply that if the consumption were to fall even further ("without the spending"), that there wouldn't be deleterious effects on the economy as a whole.
0: https://www.bostonfed.org/publications/research-department-w...