Sure, but more conservative and balanced approach still puts you in really decent shape. 4mm instead of 6 maybe.
So that's not the problem, the problem is with the idea that you start max contribution in your 20s and keep it up. To a first approximation, nobody does this.
The real way that people run into trouble with voluntary saving (tax sheltered or no) being relied on is something like this:
20s : bad salary, don't save much
30s : making better money but getting married and having a couple of kids
40s : man those kids are expensive, putting college funds together, saving a little bit. oh well at least we're building house equity.
50s : huh, we should think about saving. finally can live a bit though.
We started to hit “we could save enough to retire at 55, or 60 at worst” money just as we started having kids.
The added health insurance costs, healthcare costs (and our kids don’t even have any huge problems!), housing costs (unless we’re OK sending them to bad schools), lost wages due to time staying home caring for them, child care costs before they started school, et c… that stuff topped a quarter million before I stopped counting, and it went way higher after that.
The kids have gotten somewhat cheaper as they’ve gotten older! But having that ultra-high cost front-loaded cast like a million-plus dollar shadow on our likely at-60 savings (due to opportunity cost), not even counting the ongoing costs and the effects those are having. Retiring at 65 is now iffy…
So that's not the problem, the problem is with the idea that you start max contribution in your 20s and keep it up. To a first approximation, nobody does this.
The real way that people run into trouble with voluntary saving (tax sheltered or no) being relied on is something like this:
20s : bad salary, don't save much
30s : making better money but getting married and having a couple of kids
40s : man those kids are expensive, putting college funds together, saving a little bit. oh well at least we're building house equity.
50s : huh, we should think about saving. finally can live a bit though.
60s : oh crap, no way to catch up