Is it possible to switch instances without making a new account?

Nope, accounts exist on instances.

But you can export your settings and import them to a new account, so you keep all your subscriptions, blocks and other settings.

Can someone eli5 me the reason why you would need/want an account in a different instance? I still don't really fully understand the fediverse stuff, but am trying to.

Most common reason is you don't like how the server you're on is run, or it doesn't fit your hobbies well.
- I guess I'm not aware enough to even know how the server I'm on is run. From my understanding, you could see pretty much any community regardless of instance from whatever instance you happen to be on?
There's a variety of reasons.

instances are communities, some more loose than others

some instances have themes. lemmy.world is general, aussie.zone welcomes anyone but it's mostly Australians or friends there-of. Having a user name/address like vvilld@aussie.zone says something about you.

some instances have ideological alignments, lemmy.ml are tankies

some instances de-federate from others, like hexbear is not federated by some / many instances.

the "local" feed can be like a set of subscriptions or curated content. slrpnk.net is the best example I can think of for this, mostly environmentally conscious tech, and renewables, et cetera.

some admins turn out to be idiots. In the early days there was some support from admins of specific / niche instances for bots re-posting content from reddit.

there's no good reason not to have multiple accounts. In my own case I change instances regularly. IDK why exactly, I just actively avoid allowing my account to become some kind of extension of my identity.
Sometimes the instance you are on will block communities or other instances that you may still want to be able to view/browse.. in those cases your only solution is to create a new Lemmy account at a different instance that does not block those things.

For example you're on lemmy.world so all your blocked instances are listed at https://lemmy.world/instances

In addition lemmy.world admins also block entire communities e.g. blocking all piracy related communities is a big one there https://lemmy.world/post/13320356
- Thanks. It doesn't look like there are any blocked instances on lemmy.world. Is there a similar list of blocked communities?
You also might want one for NSFW to keep that separate
.world has had some moderation issues of late. Also, they defederated with instances they consider tankies. You think a tankie can't offer good advice when I have an AskLemmy question? Think a tankie can't offer insight troubleshooting a tech issue? I want all the voices.
- troubleshooting a tech issue
  
  Turn it off
  
  Shed the yolk of capitalism that weighs upon the working class, like they do in China.
  
  Turn it back on

Nope. Export your subs and such, import it to your new account.

Copy/paste any comments you want to archive, and that's the best you can do

Just make a new account and put the link to it in the bio of the other account. I did that ages ago and it was worth it

What’s the benefit to pawn.social?

I picked lemm.me and it seems fine.

Some servers have a particular focus. Pawb.social is a furry server. Generally doesn't matter too much which server you use as long as it's not blocked from another server where there are communities you like. You can check the /instances page to see which servers/communities are blocked by a server.

Also if you want to mod then usually best to have your acct on that community's server. Less headaches with modreports.
- It can be hard to find content if your home server doesn't interact with it enough.

Sadly there isn't which is a problem. ATPro has portable identity, activitypub does not.