ACH is short for Automated Clearing House, which is a network that exists between financial institutions. It is nothing more than a set of policies and transmission protocols that encode transactions for transfers of value. Every institution in the network has a compliance department, on which is foisted the task of monitoring these streams of transactions for what one may consider the "illegal or suspicious transaction due jour. "If you think, well that seems like it warrants a fee!" You need to keep in mind that the ACH network is fundamentally about settling transactions between banking entities, not their clients. Making sure money gets to the final account is a matter of internal process.

So you literally have banking entities parked in the chain of transaction charging everyone an ACH fee per transactions, when at the end of the day that institution jus batches those all up and does one transaction. This is called rent seeking, and it is bad in the economic world in excess.

Now. The bill payment thing. Why is that bad? Middlemen again. You're taking a substantial bill, putting a techie wrapper around it, putting it in front of people who have no idea how the financial system works, then laughing as the tubes use it, incurring an additional one or two dollars into your pocket as a toll fee for doing so.

Fintechs operate on a concept known as economies of scale. If you take a small fee from millions of people, you still get a huge pile of money in the end. You know what's really clocked the Fintech dream into overdrive? Mobile phones!

No other machine is as capable of rapidly creating a set of transaction opportunities and rent extraction than a micro computer in the presence of ubiquitous networking infrastructure! Africa literally has Internet access in places that food, clean water, and medicine aren't even givens, and the lack of consumer protections/savvy with technology have seen predatory micro-loan Fintech businesses crop up like hot cakes over there.

Fintech firms can easily hit revenue figures and profitability at orders of magnitude less capital expenditure than pretty much any other industrial vertical that actually has to move something material around. This creates a brain drain problem in capitalist/free market driven economies away from things that can make an actual material difference in the world.

Now...
The cash bit:
Have you ever wondered why 50 dollar bills are basically non-existent anymore? Why everything is in 20's at the ATM? Why there is a perpetual coin shortage?

Have you ever seen any of the stories in the news where someone goes on travel with their life savings, then ends up with them seized by a government somewhere, and having to go through hell, litigation and high water to get it back?

That didn't used to happen (in my living recollection) before a bunch of data analysis was done that came to the conclusion that the only people who do large money transfers in cash, were terrorists, criminals, or those not serviced by the government approved financial surveillance infrastructure known as banks. Thusly, travel with large amounts of cash is now seen as suspicious in and of itself. Combined with various flavors of perverse incentives and bad law that constitute the practices known as Civil Asset Forfeiture, and you're one pissed off, anal retentive bureaucrat away from having your life ruined for nothing more than trying to get somewhere.

These are no mere academic points. I've seen, scrutinized, reconfigured, and much to my regret, took part in lubricating those gears of predatory commerce. Something which I still consider myself atoning for to this day. I've sat back and watched as an actor in the space wasn't content with their profitability being as in the black as it was that year, so turned the thumbscrews jacking up the overdraft fees for day juice, while implementing other institutional policies to assure they stayed pinned to the demographic they could actually extract value most effectively from. I've seen the equity holders laughing at company parties, the misery at the call center, and the frustrations of the end users.

Do some legitimately help some small slice of their userbase? Assuredly.

Does that outweigh the damage done over time, or justify the ongoing encroachment into people's lives in terms of the ever increasing dependence of the average person on electronic, surveillable/censorable by default transfers?

No... I don't think so. Then again, I've been known to be a harbor of controversial views.