Yes. The downside is that the amount of hashpower the Bitcoin network can purchase is the block subsidy + fees. This is the "security budget". Bitcoin is only secure because getting 51% of the hashpower of the network is either infeasible or economically not worth it. Subsidy cuts in half every so often until it hits basically zero. So long-term, fees need to provide this budget. Cleared mempool = very low fees = low security budget.