In fact I can't even tell the difference between 128kbps MP3 and the CD it's encoded from, let alone superior formats like Opus or AAC or higher-bitrate MP3.
Currently at the end of the line all audio is going to be squished, at best, to 44k 16bit sampling. Most audio production and engineering is going to be taking place at quality levels than what the final CD master is, however. /During/ production working with higher quality sources such as a higher sample rate, higher bit rate FLAC sample means that you can 'do more' with it before you start running into the walls of unintended artifacts and distortions. Think of all audio processing as a destructive process - the more you have to begin with the more you can do before the destruction becomes noticeable.
Intentionally ignoring all debates on aesthetics, obviously in many artistic circumstances the artifacts and distortions are desired - but when they are you can easily achieve them in an /intentional/ way. Avoiding them is the challenge.
And there are certain contexts in which it is more noticeable: high quality club sound-systems, custom home and car audio systems, etc. My vehicle's sound system has a very easily audible difference between a 128KBS MP3 and an uncompressed 44k 16bit CD for most music, and in that context you are damn sure I want the uncompressed experience. So having an /option/ for high quality lossless formats such as FLAC available universally helps to serve such niche markets.
tldr; if you are in camp that can't tell the difference, you shouldn't download the higher quality larger files. They aren't for you. Other camps do exist, however.
edit edit: And this all ignores the annoying 'loudness war' trend in modern audio engineering to use compressors to flatten out all dynamic range anyway. Le sigh
You can convert lossy formats but there is no way to tell how the artifacts will interact.
Lossless formats do have their place but it's not as if lossy formats literally sustain bit rot; they lose information one time and that's it. Unless, of course, you convert lossy formats, but you should know not to do that.
If you do have to convert between lossy formats or absolutely need every bit of data (e.g. RAW photography) then that's one of the places you might find lossless archival storage useful. But most uses don't need it at all.
Who knows, maybe any differences I think I hear are just placebo effects :-)