One should distinguish between inflation/deflation (= the change in real world value of a token) on one hand, and debasement (= creating monetary tokens) on the other hand.

In general, a good currency has only very mild inflation or deflation, and what's more important, this mild inflation or deflation is *predictable*.  This makes that the currency is a good representation of value as a function of time, and hence a good "unit of account".   Whether the deflation or inflation is 2% or 3% ... doesn't really matter.  If you KNOW that on average, a currency has an inflation rate of 2%, say, you KNOW that 10 years from now, a given sum represents 20% less value than that same sum today, so you can take this into account in every long term agreement.  If you know that the currency is mildly deflationary, you know that a given sum will represent about 20% more than today, so that too, you can take it into account.
As such, mild inflation or deflation, for a currency, doesn't matter much, as long as it is predictable.

But in order for a currency to keep its inflation or deflation rate close to the "programmed" one, the currency OFFER needs to adapt as a function of its value.  If the currency is too expensive (that is, if the deflation is too severe), more currency needs to be put on the market.  If the currency becomes too cheap, (that is, inflation is too severe), currency needs to be taken out of the market.

A currency with a given production rate, worse, a currency with a decreasing production rate, and an increasing adoption, will be explosively deflationary.  That's exactly what we saw with bitcoin.  Everyone is cheering that bitcoin went up from $0.1 to $1700 or so in about 6 years, but that is a catastrophic deflation.  

Imagine that 6 years ago, you signed a contract with me that I would clean your room for 100 BTC (say, $10) per day, with an indemnity of breach of contract of 5000 BTC (say, $500) if you decide to stop the contract without me failing to clean your room.  Then I'm rich now, and you will be working the rest of your life to pay off the contract !
You cannot do business in such a "currency".  

If that currency would become in general usage, then the economy would fall in a deflationary spiral: as hoarding currency instead of spending it would lead to higher wealth, and as the increase in value of the hoarded currency would outpace any reasonable true economic return on investment (look at bitcoin: what real world economic investments allow a factor of 10000 ROI in 7 years !), nobody would spend, nobody would invest, and everyone would hoard more and more currency, having less and less currency running around, increasing even more the value of the few coins that are available and not hoarded yet, inspiring people to hoard even more.