I suspect most people will think you are either a total PITA to be avoided or you have a serious mental illness.

You’ll probably be viewed as weird unless you dress appropriately. Start wearing a cravat and carrying a pocket watch and see if that helps.

Speaking grammatically without using any slang or jargon will get you most of the way there, I think!

Other than in some very niche and select circumstances that I honestly can’t really think of, nobody is going to think it’s cool. However if you like it and want to do it then that’s really more important than if others will think it’s cool. However, I should add some caveats to that.

In some environments, if you’re young than school especially, can be very cruel and very conformist. In those sorts of environments, being “weird” can seriously make you miserable because you’ll be ostracised and while being authentic and true to yourself is important you’ll need to decide how important this specifically is to you, because if it’s not that important then in a context like school I’d say don’t risk it.

However if you want to try it out sometimes around friends who already like you then why not? Just try to keep an eye on people’s reactions and see if they start to get tired of it or roll their eyes or visibly cringe, that’s a sign you’re doing it too much and it’s getting irritating. Definitely don’t change your entire speech pattern to whatever you decide equates to “old timey”, all the time in every conversation with everyone, it won’t land well.

You’ll absolutely be judged.

How old-timey were you aiming? Because “it would be most wondrous” sounds more like Bill and Ted.

Learn some of those phrases, and use them to have some fun. Don’t do it all the time though. Just mix and match in a tasteful way. You can also mess around with dialects. Just don’t overdo it, because it can get distasteful very easily.

Ideally, you would find the expressions you consider useful or interesting, and start using them occasionally. For example, the Aussie style “No worries” is pretty good IMO.

Communication is a two way street.

Good communicators need to learn to pick up on how their speech lands, and learn how to adapt a little accordingly.

I doubt the internet is a good place to learn that skill. It takes a lot of real world practice, and a lot of people still get it wrong from time to time, way into adulthood.

But you should do whatever you like for yourself. But just try to be sensitive to the audience and prepared to adjust if you start to see reactions that you don’t like.

“Stop trying to make fetch happen”

Everyone has their own verbal idiosyncrasies- local dialects, accents, words and phrases you picked up somewhere that have a nice ring to them, in-jokes with your friends and family, etc.

You’ll come by them organically, no need to force it.

Inevitably, when you try to force them, at best people just won’t notice, or more likely they will notice and think you’re a weirdo, or a pretentious asshole, and at worse they might actually have a hard time understanding you which kind of defeats the purpose of speaking in the first place.

Seek out new experiences, acquire knowledge at every opportunity, meet people, go places, do things. Without even trying your speech will acquire plenty of interesting character and you won’t have to expend any effort to do so.

The real answer is that it depends on your age. Probably also race and gender. People will react differently to each.

An older adult ready for retirement? Delightful!

A kid trying to be different and impress girls! Cringey.

To answer the latter half of your question, no, people will not think you’re cool for doing this. Some will be majorly put off by it. Some miiight not be entirely too cringed out by it, but they still won’t think you’re cool just cuz of this. Your best bet is to be yourself and find the people who think that’s cool, whether that includes talking oldtimey or not.

How old oldtimey are we talking btw? Just out of curiosity lol

This is the kind of thing where the worst you can do is be a little cringy. Why not

I’ve started saying therein, thereto, therewith etc, because i feel like it makes it easier to build a sentence and it’s also easier to pronounce than the alternatives.

Just going to leave this right here

Is there a ren faire in your area? Maybe you could find one to work at, or like, a magic shoppe. It will be better received if there is a reason for you being in character.

Yeah. If you’re into it, do it. Never turn down a chance to learn something or develop a skill. Pick your audience when using a skill though. You may be able to juggle 5 balls, but a funeral probably isn’t the place. Talking like a dude that stepped out of a time machine could be cool in a bar, but not so much if you’re giving a presentation on finance.