YouTube changed a lot about their player recently.
I'll have a look in the next few days and will release a fix, thanks for letting me know.

Hi,
Have you noticed any patterns to the slowdown?
Does it happen everywhere on YouTube, or only on specific pages (like when watching a video, on the homepage, etc.)?
Edit : Try new version v2.14.1, should fix potential performances issue

Your comment is unfair, completely inappropriate and misleading.

The Add-On is 100% free for everyone and does not display any advertisements.
After 7 days of use, a single support message (toast) may appear, politely asking if you'd like to support the development. This message is non-intrusive, displayed in the bottom right corner of your screen, and can be closed at any time.
If you select "Never ask me again", it will never show up again (same if you close it through the up-right corner cross), and you'll be able to enjoy the Add-On THE SAME WAY that someone who would decide to support.

Supporting the extension is entirely optional—nobody is required to pay to use any feature.

Comparing this reminder to a virus is disrespectful to my work and unfair to other users.
No features are restricted, no user data is collected, and there are no hidden ads or malware of any kind.

The code is fully open source and can be reviewed by anyone on GitHub:
https://github.com/YouG-o/YouTube_No_Translation

Reporting the extension for this reason is baseless. Mozilla's policies explicitly allow extension developers to ask for optional support, as long as it is not intrusive or required to use the extension—which is exactly the case here.

If you have criticisms or suggestions, I'm always open to constructive feedback—but please remain respectful.

I genuinely do not understand what you are complaining about.
Does a single, non-intrusive toast like this really ruin your YouTube experience? Or is it simply the idea of reminding users that they can support the extension—the idea that my work might be rewarded—that is so objectionable to you?
In the end, seeing this reminder once (with the option to hide it forever) doesn’t seem like much to ask for someone who wants to use the extension for free.

This Add-On exists thanks to the time and effort I put in, and support messages help keep it alive for everyone.

I hope this clarification helps other users better understand how the extension works and reassures them that nothing is hidden or forced.

Thank you to all users, whether they choose to support the project or not.