[1] https://bitinfocharts.com/comparison/transactionfees-btc-sma...
[1] https://bitinfocharts.com/comparison/transactionfees-btc-sma...
In the year after the 2018 peak, fees approached zero, but in the year after the 2021 peak, they stayed higher. As long as that keeps up and they don't actually go to zero, and people are competing for block space, miners will keep lining up, and the network will be fine.
Halvings matter less as time goes on. I didn't shed any tears for miner incentives when the reward went down by 25, and I won't shed any tears when it goes down by a mere 3.125. Mining was never meant to be profitable beyond BTC's bootstrapping phase. In fact the protocol actively makes difficulty adjustments to keep profitability near zero. Let their profits go down. As long as people are competing for block space, and transaction fees keep coming in, miners will continue competing for their fractions of a percent, and the network will be fine.
In any case, neither spike was particularly long-lasting, and even if they were sustained at their peak, neither would make up for the mining incentive lost in the next halving.
And at this point somebody with huge computing power disabled could enable theirs Rig and quickly generating block to perform double-spend, and create soft fork.
If usage is high - fees will be high, and the cost of an attack will be high.
Security scales with usage, as does the incentive to attack. As long as usage trends in the same direction as value, I don't see the problem.