Often streaming sites are filled with adverts and trackers, and the videos can be problematic or just inconvenient to play in a web browser.
It is possible to stream many media sources with a separate desktop player in most Operating Systems and avoid the trackers and advertising.
FreeTube is an open source YouTube front-end with no adverts, plus optional sponsor-block functionality and the ability to download the videos or audio.
FreeTube can also be used to bypass country-blocks and age restrictions.
https://freetubeapp.io (Windows/Linux/Mac)
Media Player Classic – Black Edition comes with YouTube support built in, and can use youtube-dl.exe for more sites.
https://sourceforge.net/projects/mpcbe/
WACUP comes with support for YouTube, Vimeo, Soundcloud and Mixcloud
https://getwacup.com
Video LAN Client – VLC supports YouTube and lots more sites with addons.
https://www.videolan.org/vlc/
Spotube is an open source Spotify client that streams the audio from YouTube.
https://spotube.krtirtho.dev (Windows/Linux/Mac/Android/iOS)

You can also add YouTube decoding directly into Windows as Direct Show filters, so most media players that can use web addresses and system CoDecs can play them (inc. Windows Media Player and VLC).
It is very easy to install if you use the exe installer version.
3DYD Youtube Source
https://www.3dyd.com
When used with youtube-dl.exe it supports many other sites.

Exponentially expand the amount of sites supported by 3DYD Youtube Source & MPC-BE with youtube-dl.exe
https://ytdl-org.github.io/youtube-dl/ – [Huge list of supported sites]

Android

For Android, NewPipe is an open source Youtube player with many useful features inc. the ability to save video or audio files and work as an audio only player.
It can also use alternative decoding engines such as VLC.
https://newpipe.schabi.org

EXTRAS

Using Cytu.be you can watch synchronised media from many sites but with other people in your own private or public virtual cinema. Includes chat and customisation, and can be self-hosted.
https://cytu.be (open source)

3DYD Youtube Source can also use FFMPEG if it is installed.
https://ffmpeg.org/download.html#build-windows
This is generally used for splitting, joining or re-coding media content.

If you have youtube-dl and FFMPEG you may as well have a handy interface to use the download capability. There are a few tools called youtube-dl gui but I chose this one because of its small size and ease of use.
https://github.com/murrty/youtube-dl-gui
For convenience I keep all 3 of these together in the FFMPEG folder I made in my Programs Folder.

The manual install instructions for FFMPEG include adding the location to your System Environment Variables. If you do not know what this is or how to find it you may prefer a convenient tool for editing this info.
Windows Environment Variables Editor
http://eveditor.com/tour/
Even if you do know how to edit the ENV variables you may appreciate the functionality of this tool.