That means that if block subsidy was cut off completely, then the hashrate would probably drop by 90 to 95%, from currently around 600 Eh/s to perhaps 50-70 Eh/s. You may say that's dramatic, but that is approximately the hashrate Bitcoin had in 2018/19 (
see this chart), and Bitcoin was considered safe at this time too.
The mining hardware has improved by 8x since 2018. Back then miners were using S9 which was able to produce 14Th/s with 1373W of power. Now with the S21 XP HYD you can get 473Th/s with 5676W of power. S9 = ~0.01 Th/J and S21 XP = ~0.08Th/J. So effectively, 50-70Eh/s hashrate now a days is actually equal to 8-10Eh/s in 2018. Also the market cap of Bitcoin is 4x higher than in 2018. So to have the same market cap to security ratio you would need 4x the hashrate/power consumption of 2018 hashrate. So if the hashrate did fall to 50-70 Eh/s then the security of the network in relation to the market cap would drop 24x