Performance matters, but at least initially only as far as it doesn't complicate your code significantly. That's why a simple static website often beats some hyper modern latest framework optimization journey websites. You gotta maintain that shit. And you are making sacrifices elsewhere, in the areas of accessibility and possibly privacy and possibly ethics.
So yeah, make sure not to lose performance unreasonably, but also don't obsess with performance to the point of making things unusable or way too complicated for what they do.
Notably, this is subjective. I’ve had devs tell me that joins (in SQL) are too complicated, so they’d prefer to just duplicate data everywhere. I get that skill is a spectrum, but it’s getting to the point where I feel like we’ve passed the floor, and need to firmly state that there are in fact some basic ideas that are required knowledge.
Yes, at the most absurd limits, some autists may occasionally obsess and make things worse. We're so far from that problem today, it would be a good one to have.
IME, making things fast almost always also makes them simpler and easier to understand.
Building high-performance software often means building less of it, which translates into simpler concepts, fewer abstractions, and shorter times to execution.
It's not a trade-off, it's valuable all the way down.
Treating high performance as a feature and low performance as a bug impacts everything we do and ignoring them for decades is how you get the rivers of garbage we're swimming in.
So yeah, make sure not to lose performance unreasonably, but also don't obsess with performance to the point of making things unusable or way too complicated for what they do.