Spent the last decade thinking about this.

1. Interest rates are falling to zero everywhere
2. P/E ratios are increasing
3. Low inflation has some hidden variables that are not infinite

When interest rates fall we can afford to borrow more. Past models were developed when interest rates fell 20 or 30% because that's what the rate cuts represented. Now we are cutting the rates 75% or more from 1.75 to 0.25 instead of from 7% to say 5%. The cut from 0.25% to 0 will be close to infinite in terms of percent or how much we can afford to borrow if it's never amortized or paid back. My guess is it won't be paid back since we all know there isn't ever enough money to pay back a fractional reserve.

Watch Price to Earnings if you want to make money. They don't make sense any more traditionally and a lot of amateurs are investing thanks to self-directed platforms, this can and is being exploited. Low rates are forcing people into the markets and they are being farmed by professionals.

Regarding inflation I need to write a post on this, let's just assume the model is completely wrong and unsustainable. Eventually the price of essentials will spiral out of control and the substitutes will be very poor. While TV's get better and cheaper the quality of food gets shittier. The price of fresh produce will be the first thing to spiral out of control. Plant a garden.