I beat Fallout 1 on Steam Deck
The blog can't all be technical nonsense, now can it?
After ~36 hours, I beat Fallout 1 on my Steam Deck. (Warning: some spoilers ahead for this ~28 year old game.)

Whoops, wrong picture.

I apologize for the iPhone picture instead of proper screenshots. I was too lazy to figure out how to take screenshots on Steam Deck and then figure out how to export them.
Anyway. If you look online, people will tell you that Fallout 1 is an incredibly hard game. But the truth is, it isn't. Factually, any game where you can save and load at any time is not that difficult. Also, you can look up what to do online; it's a popular game so there's plenty of information.
Personally, I made it a point to try to avoid spoilers, only looking up stuff when I got stuck. One of the difficulties of Fallout is that it can be a bit of a "where do I go" kind of game. While the game is "open world" in theory, you probably should play it in a certain order. I spent a lot of time trying to clear out The Cathedral and struggling intensely, and I didn't get to Necropolis until pretty close to the end of the 150 day deadline. By that time, clearing out Necropolis was trivial.
But I think the main difficulty for people is the "dated" gameplay and controls. However, after playing the game for long enough, I was able to adapt. If you don't know what you're doing, you might be killed by rats in the first cave, which is a frustrating experience. But, if you know what you're doing, then that probably won't happen. If you put in the effort, you will build the intuition needed to play the game.
Another pain, on the Steam Deck particularly, was playing without a mouse, and on a small screen. Most of the GUI elements were pretty small and have to be accessed using the mouse, and using the Steam Deck trackpad was annoying for it. Trying to carefully move the mouse over a tiny button again and again was incredibly frustrating... until it wasn't. After doing it enough, I got quite good at clicking the tiny buttons.
So, the gameplay takes some effort to understand, and the game has some accessibility difficulties. But the most annoying thing is the occasional bugginess. For example, there's a few opportunities for your NPC companions to get you stuck. It's not just this bridge; I got stuck once or twice in tight indoor areas because of them cornering me.
Companion NPCs are also just dumb. Beyond the early game, they tend to get in the way more often than they help. There are some mods to fix them, but obviously I didn't look into mods until I beat the game. But there was one bug that really did break the game:

I don't know how I triggered this bug, but once I did, my save was corrupted. I could restore the save, but I couldn't leave the square I was in without getting the same crash again and again. So I had to restart. Luckily, this was my only game-breaking bug.
Let's get to the good: this is just a great game. Once I started playing it, it was very hard to put it down. I loved exploring the world, I loved fighting when the fight was balanced, and I absolutely loved the art and atmosphere. I know some people don't love the art of old games like this one, but they're completely wrong. The art has far more soul and beauty than any triple A game released in the past few years. I don't want to see a remastered version of OG Fallout; it is perfect as is.
I can't speak much about replayability, but I hope to one day play around a bit with different RPG attributes. One of the cool things about Fallout is that you can try to play it a number of different ways, whether more combat-oriented, stealth-oriented, intelligence or charisma-oriented. As linked, high or low intelligence can make the dialogue and thus overall game completely different.
So anyway, you should play it too. You can get the Fallout Classic Collection for $20, which includes Fallout, Fallout 2, and Fallout Tactics. But if you wait for a sale, you can get it for like 80% off. I hope to try Fallout 2 soon, but I expect I will become utterly addicted to it too, so I will put it off for now.