I think it can be rational for an investor to forgo productive assets, even if they have no opinions about market timing. They might look at a company, estimate

I think it can be rational for an investor to forgo productive assets, even if they have no opinions about market timing. They might look at a company, estimate its lifespan, estimate its total inflation-adjusted earnings over that period, and find that it's less than the current market cap. In that case it's just not a good investment opportunity, irrespective of market timing. Historically there has always been a shortage of capital, and plenty of productive enterprises competing for that capital, so investors have received a discount on expected future earnings. But I think the case can be made that in the current economy, there is no such discount. That appears to be Buffet's stance, judging from his public comments. He says that he doesn't practice market timing, but simply can't find many worthwhile investments.