In the beginning of the pandemic, everyone and their mother decided they were going to rescue every pet they could lay their hands on. I'm not saying I'm any different here - I'm just saying its time goldfish had their adult-renaissance.
It's unfortunate that at most pet stores goldfish are seen as inferior - they are never in any of the "showy" tanks along the walls, and rarely even ever have substrate (gravel or sand) in their tanks. They may not have a tank light, are absolutely packed into the tank, and are sold as feeder fish. But I'm here to tell you that there are plenty of reasons to appreciate these lovely creatures on their own, and that taking care of them is really no different than any other pet.
One of the first things you'll find online is that you need absolutely no less than a 50-75 gallon tank for your goldfish, and in part, this is true - but not for every type. Many fancy goldfish do not get nearly as big as "common" goldfish, and need no more than a 20 gallon tank. It should be noted that no goldfish, or any fish for that matter, should ever be put in a bowl. Fish bowls are too small for any fish, and the stagnant water and small space are very unhealthy. Think about where you would want to put a dog or cat - would you want them in a stale old room that's barely bigger than they are? And may very well be smaller than they are when they're fully grown? It's the same with fish. A good filtration system, and clean, cool water with plenty of growing and swimming room is key to their happiness and healthiness!
While on the subjects of tanks, however, don't buy your tank and your fish on the same day. They tank needs time to get settled before the fish is plopped in. There's a lot I could tell you about cycling a tank, but in short: fish poop, and the water from your tap isn't going to be able to handle that right off the bat. Too much poop in the water, and you have a dead fish on your hands. Let your tank sit and filter through for a long while before you get those goldies.
Personally, I'm not the person to point at one specific fish and tell the poor store clerks to chase it around for an hour. All goldfish have slightly different coloration, and that's the fun of it! Getting to know their colors and spots and stripes is just that same as that on your cat. Plus, as they grow, their coloring may very well change! These fish can live upwards of 20 years, and the oldest on record lived to 43; so you'll be able to know every side of your fish with all that time together.
But with so much precaution that needs to be taken, and the amount of time and growth, what's really the point? Where does the fun come in? Every step of the way! From picking out what you're going to put in your tank, to what type of tools you want, to what type of food your fish eats, there's a lot of customization options at your fingertips. Picking décor, substrate, real or fake plants is always a great time, whether you're doing it alone or with family or housemates. A great option (if it's available to you) is having a friend with a tank give you a piece of décor from their tank, or even a filter - it will jump start your tank's cycle way faster than if you're starting from scratch.
Once your fish is in the tank, don't be surprised at their initial nervousness. They've just moved house, and don't exactly know why, how, or where they now are. When they get acclimated, then you'll see their personality shine through. I learned very quickly that my goldfish does not like the tank light to be on for very long, and much prefers the natural light from a nearby window. He loves to do laps near the front of the tank, and explores the plants when he's feeling brave. When he's tuckered out, he'll rest for a while either in the back corner, or right in the middle of the tank, always facing the window. He knows that mornings are when he gets to eat, and gets very excited, bopping his nose up out of the water when I first walk into the room. All of these things make him just like any other independent pet you could have outside of water.
So don't be nervous by what the internet may scare you with about goldfish having a huge bioload or being fast growers - while these are true, they are not harmful facts, and just mean you get to spend a bit more time caring for your fish. A beautiful, well kept goldfish tank is a great centerpiece to any room, and will impress any guest with your adult spin on this "childhood" pet!
Author note: This is not a comprehensive guide to fish keeping. This is my experience, and the "fun side" to keeping a goldfish. I did not cover all aspects of care in depth. This is not advice, nor for education.