I've used Shotcut, and it was easy to use, and its simplicity reminded me of iMovie, which I also recommend for beginners. KDENlive was also good enough for most projects. As stated by others, the biggest weakness is that these editors are based on MLT framework. But if you cut videos once in a while, these are fine.
As for me, I edit a lot more videos, and I spend a quite of time on doing it. I've tried to work with a lot of different FOSS video editors, except Blender, and my conclusion was always the same -- it's usable, but a little rough on the edge, and has just enough minor bugs or quirks to be irritating and sometimes frustrating. I'm not talking about just crashes, since that happens on all video editors even on Premiere Pro.
Video editing is somewhat similar to coding, as it requires a lot of concentration, intensity, and creativity... There's nothing more frustrating than having the software/tools that gets in your way and block your flow and progress. Also time is money in video production house, often with tight deadlines. Some wedding videographers are offering same-day edits, which sounds insane to me, since video editing takes a lot of time. As for me, it takes about 7 hours to edit 1 hour video.
Currently I'm using Davinci Resolve 14 (on both Mac and Windows but haven't used on Linux yet). So far, it has worked surprisingly well. I really like the built-in audio editing and coloring tools. All this is free, with exception of some features for pro/studio version.
Some have complained the lack of h264/265 import on Linux version of Davinci Resolve, but you can always transcode to "pseudo-lossless" codec such as DNxHR/DNxHD (or ProRes if on Mac) using ffmpeg first. This step is usually automated using script to convert raw footage. Most pro workflow also involves this extra step, because editing on h264 source is really painfully slow and inefficient.
As a side note, the last time I checked, in LA/Hollywood, Avid was still the king of editor, but it may be changing. Anywhere except Hollywood, Premiere Pro CC is definitely the most popular editor, especially when it's used in conjunction with After Effects. However, I didn't need AE and I didn't like subscription-based payment model. Avid Composer First is free version of Avid, but it can't output 4k, and Avid UI is horrible.