How do you define reliable?
Do you just mean uptime, or how about this,? The ability to do what you want when you want without services falling over?
Imagine being able to download whilst watching Netflix, Twitch etc., no drop of resolution or buffering. To me thats as much reliability as is service uptime. All without no QoS meddling on local setup.
Thats the real advantage, a connection that you wont or will rarely saturate, meaning everything just works.
I used to download and watch netflix or equivalent when I was on 36Mbs FTTC, downloading was not so fast, but it worked, as long as you remember to restrict it over wise it will take as much as it can and Netflix will have nothing, and it can still do that with higher speeds broadband.
As you said, the advantage of higher speed broadband is the bandwidth available to do more things faster, which for a lot of people will not make one bit of difference.
I bet if I went to the majority of people I know and had 1 Gb/s FTTP broadband service put into their house, they would not even notice, even those with a few people living there. Why? Because the majority of people use their broadband for streaming, maybe connecting their phones or tablets to and even those with computers, I doubt download large files.
All this you need 1Gb/s is a marketing ploy and now some people can get faster speeds, that will be a marketing ploy to get people to part with more money for a service they don't need.
My eldist brother have dropped from 500Mb\s to 120 or something like that, because it is cheaper and while he does download now and again for bits for Abaleton live, he don't stream as he is not a TV person and he may browse for different things and that si about it.
My partner have dropped from 900Mb/s to 200, realising that she never needed that speed.
Sure if you are going to make use of the speed then there is nothing wrong with going for it, not sure if anyone really need 5Gb/s, that would take some using, unless you have around 30 people in the same building using it at the same time, and then you need the internal network to cope with it which is another problem.
Internet providers will talk people into getting these faster speeds, because you can do everything faster, but the user will not do be able to do anything faster as they have not got the equipment to do it, even if it did make a difference.
Video will only stream so fast, music takes very little even high def, browsing, people will not notice any difference, reading their emails, texting with WhatsApp or RCS or any other thing like that is not going to make their text get to the other person any quicker.
You get to a certain point where things are so fast, you notice little difference, the ones on here on about ZX81, or about more than 640K of ram and faster CPUs, if you're going down that road then you can say, why did we come off dial up or ADSL. Apart from the odd thing, like games because they tend to use faster tech, if I stuck to say my AMD ryzen 7 1700 based computer in front of you or many people to be honest and also a machine with a AMD Ryzen 7 8700F, with the same amount of ram in and maybe the same video card. You would say the 8700 on benchmarks would be a lot faster than my old CPU and you would be right, it is. But would you notice in normal use?
Even video editing, the difference is minimal, maybe 30 seconds longer on the older machine to render on a 1-hour-long video. If you are just browsing and doing a bit of office stuff, you certainly would not notice.
That is why I am dithering to update my PC, it is only used for games mainly these days, but older games, it works, sure it is 8 years old now, well the board, CPU and some of the memory is, but for the most part it is still workingish.
Just trying to get though that a lot of people would not notice any difference in speed whatsoever. As for reliability, if it does what I need and works when I want it to, then that to me is reliability.
Sorry about it being so long.
Adrian
Desktop machines Mac mini pro with macOS Sequoia, also pc Ryzen powered with windows something or other.
Zooming with Zzoomm FTTP,