One of the classic bits of advice for writers in different media is "show, don't tell." Don't say the guy's rich and generous; have him flip a $20 to the delivery guy.
It is often good advice; I've given it lots of times as feedback.
It's not always
good advice. Sometimes it is far more effective to tell than to show.
For example, in JAWS, Quint tells the story of the sinking of the Indianapolis
... Eleven hundred men went into the water. Vessel went down in twelve minutes. Didn't see the first shark for about a half an hour. Tiger. Thirteen footer. You know how you know that when you're in the water, chief? You tell by lookin' from the dorsal to the tail. What we didn't know... was our bomb mission had been so secret, no distress signal had been sent. Huh huh. They didn't even list us overdue for a week. Very first light, chief. The sharks come cruisin'. So we formed ourselves into tight groups. You know it's... kinda like ol' squares in battle like a, you see on a calendar, like the battle of Waterloo. And the idea was, the shark comes to the nearest man and that man, he'd start poundin' and hollerin' and screamin' and sometimes the shark would go away. Sometimes he wouldn't go away. Sometimes that shark, he looks right into you. Right into your eyes. You know the thing about a shark, he's got...lifeless eyes, black eyes, like a doll's eye. When he comes at ya, doesn't seem to be livin'. Until he bites ya and those black eyes roll over white. And then, ah then you hear that terrible high pitch screamin' and the ocean turns red and spite of all the poundin' and the hollerin' they all come in and rip you to pieces.
Y'know by the end of that first dawn, lost a hundred men! I don't know how many sharks, maybe a thousand! I don't know how many men, they averaged six an hour. On Thursday mornin' chief, I bumped into a friend of mine, Herbie Robinson from Cleveland. Baseball player, boson's mate. I thought he was asleep, reached over to wake him up. Bobbed up and down in the water, just like a kinda top. Up ended. He'd been bitten in half below the waist. Noon the fifth day, Mr. Hooper, a Lockheed Ventura saw us. He's a young pilot, a lot younger than Mr. Hooper, anyway he saw us and come in low. And three hours later a big fat PBY comes down and start to pick us up. You know that was the time I was most frightened? Waitin' for my turn. I'll never put on a lifejacket again. So, eleven hundred men went in the water, three hundred and sixteen men come out, the sharks took the rest, June the 29, 1945. Anyway, we delivered the bomb.
There are a bunch of reasons why you wouldn't want to, and couldn't, show this.
For one thing, sheer scope. JAWS was shot on a budget. Shooting a couple hundred guys in the water would be a massive endeavor.
Second, passage of time. Part of the horror of this story is imagining being stuck in the water for days and nights and days, not knowing if help was coming, not knowing if you were next. Film, in particular, is rubbish at communicating things changing over a period of time. You can show shadows moving. You can show seasons. You can show pages flying off a calendar (but who still has a calendar?). But how do you fast-forward on hundreds of guys in the water for a couple of days? A series of dissolves? Ugh.
Third, number. Stalin said, "One death is a tragedy. A million is a statistic." (He murdered millions of people.) If you tried to show hundreds of deaths, all you'd do is inoculate the audience against feeling anything about the next person to die.
Fourth, extreme graphic violence. Except in a gore horror film, the audience generally does not want to see someone bitten in half. Rather than being horrified, a lot of people would feel nauseous.
Fifth, attitude. The point of the story is not that sharks eat people. We knew that. The point of the story is that Quint fucking hates sharks.
So, Spielberg and writers Benchley and Gottlieb have Quint tell the story. It's a hell of a speech.
So, yeah, sure, it is often much better to show than to tell. It's fair to say that before you give a character a big ole chunk of exposition to tell, you should consider how to show the same information. Expository dialog, like readables in games, can become a crutch.
But don't be afraid to have a character tell a story: if it's too big, or takes place over too much time, or is something so over the top the audience would really rather you didn't show them. Or if the point of the story is what it means to the story teller.