No widespread adoption is exactly what makes it a bad currency.
It makes it a young currency, not a bad one.
Bitcoin is slower than every current electronic payment (credit card, ACH, wire transfers are accepted in seconds vs. 10-60 minutes for bitcoin)
I can broadcast a bitcoin or a credit card transaction instantly. After 10-60 minutes, I can no longer reverse a bitcoin transaction, whereas I can reverse a credit card transactin for up to 180 days depending on the provider. The recipient can spend the bitcoin instantly without waiting for a confirmation if they choose, whereas it will take several days for the credit card company to pay them the fiat they are owed.
lower fees is a big nope for credit card and ACH.
Credit card transactions cost 2-3% in fees, which could be hundreds or dollars. Bitcoin transactions cost a few cents.
People using bitcoin for actual commerce are the vast minority of people involved in bitcoin. Glad you find use in it as a currency. I'm not expecting that to go mainstream any time soon.
And yet, if nobody used it as a currency then it would have zero value and nobody would be speculating on the price. Using it as a currency drives adoption, and adoption drives price increases.
It doesn't matter why there isn't widespread adoption, the fact that it isn't there makes it a bad currency. You are probably of the opinion that will change. I'm undecided, but the fact remains that while there isn't widespread adoption, it's a poor currency.
Immutability doesn't make something instant. You can't reverse credit card transactions without cause. There are enough safeguards in place that people who attempt to abuse that system won't be able to very long, and as the middleman, the credit card company takes on the liability of being in the gray area. Payment reversals are not so prevalent that bitcoin becomes a superior payment method because of it.
I've never paid a transaction fee for using a credit card or ACH. Assuming that bitcoin transactions only cost "a few cents" (which in the vast majority of cases is not true), zero is still less than that.
We've seen plenty of evidence to disprove your last point. Bitcoin is overwhelmingly not used for commerce and yet there is immense interest in it as an asset class. These things are definitely not related in this case. There is a not insignificant number of people who FOMO buy it at this point cuz they want those sweet moon gains. (Or so they've heard.)