Let's say you bought a bitcoin for $1000 in January 2018.
So you have to beat inflation and also the performance of other investments to say that your Bitcoin investment was a better investment, than other alternative investments.
Let's say your inflation is 5% and your best return on some other investment is %20 per year, then your Bitcoin price increase will have to be more than %25 to beat the alternative investment.
Let's say you hoard for 5 years, then you would need a price increase of 125% to beat your alternative investment returns over 5 years.
So we cannot have a price increase of 800% in year 1 and then a price decrease of %400 in year 2 and another price decrease of 200% in year 3 and so on...
Hope you get at what I am saying. Hoarding might be harmful to your profits, if you do not cash out SOME profit on the ATH.

..... You might end up with a bitcoin worth $100 in year 5.

While you are correct when you say a constant growth will be good for bitcoin especially for all of those that see bitcoin mostly as a form of investment, at the same time you are setting the bar too high, while there are many investments that can give profits of 20% per year most people do not know how to find them and so the average profit should be something between 2% to 8% per year and that is an amount bitcoin can easily give each year.