Is not immoral to charge interest on money lending, is just the way money works as it is today.
But money is not a product, is more like a contract between all its users. And that contract can be flawed and lead to undesirable effects.
Money is artificially scarce and is the only capital whose yields cannot drop to zero by competition. Ironically is also the only capital that doesn't produce anything of value.
The difference is that profits disappear by competition and capital yields are artificially maintained "high" by the current design of money.
Simply by competing "dishonestly" with other capitals. The accumulation of every type of capital stops when that type of capital yields less than money itself (which as said doesn't produce any good or service on its own).
Pretty much everything you said there is equally applicable to any kind of scarce resource, like oil, steel, or gold. They are all:
- traded on contracts
- are all scarce
- all "don't produce anything of value" (they can be used as ingredients in production, but are not productions of value in themselves)
- Their yields can not drop to zero by competition (way more demand than supply)
- All have the potential stop accumulation of other types of capital when opportunities to invest in these commodities exists
And like money, many of these commodities can last almost for ever, too.