CapCut is definitely enough for YouTube if you know what you're using it for. The most important thing: export quality. If you set the highest resolution in the settings (ideally 4K, but at least 1080p at 60fps), you'll get a video that's technically just as good as one from a desktop program. The app has pretty solid editing, effects, and color correction tools these days that are completely sufficient for most YouTube content.
The real difference isn't in the app itself, but in your workflow. On a laptop you've got larger files, more storage space, and a better overview when dealing with more complex projects - that makes long sessions more comfortable. If you're working a lot with multiple video tracks, transitions, and color grading, you'll quickly realize that CapCut on your phone has its limits. But for straightforward cuts, music, transitions, and text? No problem.
My tip: just use CapCut and see if you're happy with it. If the videos look good and your audience likes them, you don't need anything else. You can always switch to a desktop program later if your standards grow or the projects get too demanding.