For the record, since the introduction of WebGL in 2011, Construct games have rendered almost identically to native games. WebGL is basically OpenGL exposed to the web. So it's basically using the same rendering API as any other native game using OpenGL. (With WebGPU, this analogy will continue, but being more or less equivalent to the next generation Vulkan/Metal/DX12 APIs.)
The main difference introduced by browsers is the driver blacklist. There are many poor quality drivers out there. These can crash and glitch and ruin games. This is a serious problem faced by many native engines. There is little anyone can do about it. Sadly the state of graphics drivers continues to be poor. (Hopefully the next generation APIs help with this, since they allow the drivers to be much simpler.) Browsers blacklist known bad drivers so you get software rendering instead. This means the game runs correctly, but slowly.
So barring some kind of obscure browser bug we don't know about yet, the only explanation seems to be the graphics drivers. These are still a problem no matter which technology you use. You may find that when using some other game engine, it seems to be faster, but then you later run in to the crashes and glitches that the browser makers were trying to avoid. This can cause even worse problems, such as the game crashing or just showing a black screen on various types of Android devices.
So while you may claim that Android performance sucks, I think really this is just driver blacklisting on a small number of devices for a good reason. It's a matter of picking your poison - do you want software rendering or the risk of crashes and glitches? I think the former is the right choice.
Changing the framerate mode will only make this worse. It doesn't make anything faster, it only changes when frames are scheduled. Unlimited framerate mode will allow powerful devices to run up in to the hundreds, or even thousands, of frames per second, promptly drain the battery, and earn you poor reviews.