What kind of security level does TLS provide, as of 2019?
Quite a good security level, under the assumption that the configuration is according to best practice. I'll try to explain what I mean using lay terms. This means I will stray a little bit from technical accuracy to make it more understandable for people who may not have a lot of experience in security.
TLS is not like Coca-Cola, it's like Steak!
When you go to the grocery store, and you go buy a can of Coca-Cola, you expect it to taste exactly like all the other cans of Coca-Cola you have ever drunk before. TLS is not like that! TLS is more like Steak. You had some good ones, you had some bad ones, and all of them taste different, depending on the meat and on how well it was cooked.
What that metaphor should show is that a question like "Is TLS secure?" is akin to asking "Does steak taste good?". The definite answer is maybe! You can have TLS that is considered very secure, and you can have TLS that offers no security whatsoever. Just like how you can have steak that tastes so amazing you will talk about it for a while, and how you can have steak that tastes like somebody put a shoe sole on a grill.
When do I know if TLS is secure?
The meat of TLS
TLS is based on ciphers, just like steak is based on meat. A cipher is a fancy term for throwing a bunch of cryptographic stuff together, but the details don't matter for a lay explanation. The first ciphers we made were bad. We didn't know how to made good ciphers, but we eventually learned from our mistakes. Modern ciphers are considered "more secure" than old ciphers, because more knowledge went into the new ones than into the old one's. (Just like how the first steak a chef cooks will not be as good as the 1000th steak).
TLS is considered secure, if it only allows good, modern ciphers. Old, bad ciphers can cause problems!
What does it take to attack TLS?
It depends on the ciphers being used. In the absolute worst possible case, this means that TLS is configured with a NULL cipher, meaning that no encryption or authentication is done at all. This shouldn't be accepted by clients anymore today, but if you run a very old and outdated system, it might.
In a more realistic "worst-case", it could be that TLS is configured in a way to use weak ciphers. While these ciphers are not trivial to crack, a sufficiently advanced attacker (think NSA, etc.) can certainly do it. If really weak ciphers are chosen, then even less sophisticated hardware may be necessary.
Should I, as a normal consumer, worry about TLS?
Most likely not! Modern phones and operating systems are configured in a way that they only allow good ciphers. The chance of an attacker being able to crack one of those to sniff your traffic is very, very, very small. It is currently not known if any of the Alphabet Boys (e.g. NSA, etc.) are able to crack any of those ciphers.
On the other hand, if you use Android 2.3 or Windows XP, then it is time to upgrade to something more recent. Aside from the numerous other reasons for switching away from a long obsolete system, these operating systems don't support any modern ciphers. To fit with our analogy, they're like a store that only sells horrible old "meat".
The only time you should worry is when you see errors related to TLS. It is most likely an error on the side of the server you are trying to connect to, but it might also mean someone is trying to spy on you.