How f*cking shoddy is that?
We're building the modern world on computers and that's the best we can do?
No matter what university lecturers say (at least mine did 25 years ago), CPU isn't
cheap, memory isn't
cheap, storeage isn't
How often do people complain about how much memory, or CPU, or disk (not so much disk in this case) browsers use up? It's always a tradeoff between memory usage and CPU cycles. Sure, they could have mechanisms to identify pointers vs integers, but that'd take more memory to do, a flag/mark isn't magically 0 bytes of data, it'd have to take up some amount of bits/bytes in the data structures, the millions of data structures thus taking up even more RAM in the already bloated RAM usage of browsers. Each flag might be tiny, but even a tiny number multiplied by millions becomes a big aggregate number.
Alternatively (RAM vs CPU tradeoff), they could have more smarts and try to work out dynamically (and transiently, remember, we aren't storing this knowledge in RAM beyond the GC cycle in this case, as opposed to the previous one) at GC time whether it's a pointer or an interger, taking, say, 20 cycles to do it, millions of times over on a GC. And like with the flag in memory, even a tiny number times millions of iterations in a GC will be a big number, being multiple seconds of processing on what people want to be an instantly-responsive system. Thus taking massively more CPU on what people complain are already CPU-hogging processes.
So they chose an RAM/CPU optimsed method, but if you don't do a CPU vs RAM tradeoff, the tradeoff comes from somehwere else. And as a consumer, would you rather your browser hangs continually for GC (excessive CPU), takes significantly more RAM (do you have enough RAM? How many tabs/windows can you now have open? How many other apps can you have running in the background?) or uses what was at the time thought to be a secure alternative method because of ASLR mitigating the issue?
From a developers perspective, this is definitely a damned if you do, damned if you don't scenario.