A bit off topic but yes, these days "native" apps tend to be memory hogs. Modern computers have tons of CPU and memory which makes the developers lazy, it would seem. Generally, noone optimizes their desktop clients.
Telegram is amazingly smooth on Linux and Windows.
Because it has a real native backend. It uses Qt/C++. I really wish other chat apps would do it...
I've had Telegram, Slack and Discord open all day. Currently, they're using: 7MB Telegram, 350MB Slack, and 140MB Discord. Other heavy things I've got running are 160MB Spotify (which is electron) and 1GB Firefox (which is doing actual work with its memory).