It seems rare that a Chinese flashlight has a simple on -off switch. They are usually encumbered with 2 to 5 "modes".
This is a detriment to functionality.
I have to respectfully disagree. Modes are wonderful for most users and enhance the functionality and versatility of a flashlight. In my opinion, it is with only a specific type of flashlight application in which various modes can be detrimental unless a user interface "hides" them. That type is the tactical flashlight. Hence, it's common to see flashlights from Surefire, Elzetta, and the like with only one or two modes. These are often designed specifically with tactical usage in mind with their targeted customer base being law enforcement, military, and those who want firearm lighting. In this regard, simplicity and direct access to full output makes a lot of sense. However, these hardly make ideal flashlights in other tasks ranging from household duty to outdoor lighting due to the lack of modes to suit the output to the specific task.
How the Chinese brands differ is that they make their products with much more versatility in mind. They focus on outputs, modes, and features to cover a broader spectrum of usage. I personally own a number of tactical lights but find that the models with more modes are more useful for my primary application; outdoor nighttime activity lighting. This primarily includes night hiking and camping. In this regard, you want various modes so you can control the appropriate output and run times. You really don't want full output while trying to find something inside your bag inside a dark tent. You also don't want to compromise your night vision with something too bright when you need to see something close up. However, you want the same flashlight to illuminate downrange to light up a path, object, etc. Modes give you that flexibility while helping to preserve battery life.
In the past, before LED flashlights were available, I used to use one-mode tactical flashlights when camping in addition to large Maglites. Now, I can carry a small LED flashlight that can handle just about any task due to its modes. From a sub-lumen moonlight mode to nearly a 1000 lumens for range illumination, modes allow a single flashlight to handle most tasks. In this regard, I greatly appreciate the approach Chinese brand have taken all while offering a very good value.
Lastly, it's not like it's one or the other. Some UIs have take the approach to "hide" their modes or program the flashlight to your usage or liking. Some flashlights now only have 3 main modes (L,M,H) with special access to others like strobe, SOS, Turbo, etc if desired instead of being in the main cycle. Others like my Klarus XT12GT allow you to program the flashlight between "Tactical" or "Outdoor" mode, changing how the buttons work with direct access.
With all of these realities in mind, I can't say modes on Chinese flashlights are a bad thing at all for most people. However, if one truly desires a simple interface for maximum reliability and predictable output, then there are products specifically made for that purpose, especially by American manufacturers who focus on specifically tactical applications.