the percentage of replies you get on "introducing" yourself is very very small. Should you send a large number of "hello" type messages or meticulously send personalized messages to individuals? because it does take a lot of time to write such messages. and I never got good results with such an approach.
My honest opinion is that all the people that complain about matches only writing "Hi" or "How's your day?" don't care how brief or simplistic the message is if they find their match attractive. In fact, I think 99.9% of the things you hear single men and women call out as unacceptable depend heavily on how good-looking or not good-looking they find their match.
This is one of the biggest mistakes single people make when dating online. They excuse lazy or even bad behavior because they find the other person hot. They engage the aforementioned lazy boor and are shocked when, a couple weeks later, they're texts are left on read or their match evades any suggestion of meeting offline.
I do not recommend writing a bunch of cut-and-paste "Hello" messages. While it's still an opening, it's one that shows you made no effort. That won't work, as many dating app users want to feel special. (Yes, I'm talking to you, too, guys.) The fact their match is a stranger doesn't matter. They want to feel as though the other person found them unique enough that they want to impress them. Whether this is rational or not is inconsequential. Most people know a customized intro message is ideal. However, you don't have to write a novel.
Three lines. That's it. The first and the last can be copy pasted. The second MUST make it clear you read their profile.
Hey, Anna!
Looks like we matched. [Statement that includes a reference to their profile.] Take a look at my profile and drop a line back if you'd like to chat.
A response like this contains a healthy word count and a clear directive to respond should your match like your profile.
It's important to realize that, just because someone swiped right does not mean they read your entire profile or viewed all of your photos. At this stage of the game, nobody should be automatically expect to hear from their match simply because mutual initial interest was shown. You must appropriate your expectations where this is concerned. Only if someone responds to you or initiates communication can you be relatively sure they've seen your full profile.
Good luck!