I'd take guaranteed 100Mbps without outages over best effort 1Gpbs any time. Unfortunately, it's hard to get this service at reasonable consumer prices, at least in Germany
To improve reliability, you can use multiple services from different vendors and implement automatic roll-over with Mikrotik and the likes. This is something I have been doing back in the day for the enterprise I am still working at.
I did it at home as well. At least 2x more money to pay, but it was worth it because my bread and butter depended on having stable internet connectivity.
I think here in Czechia they must guarantee 60% of paid speed, so with 1Gb internet the worst you must get is 500-600 Mb
I saw yesterday some German ads while watching F1 and the prices were insane like 8-30x higher than in Czechia and they were not ashamed to advertise it, here I pay 12€ in Prague for fiber 1Gb and it's so expensive because I'm not using directly my ISP infrastructure bit be rents it from power supplier, otherwise it could be 10€, it's odd since mobile data prices are much more expensive here than in neighboring countries
The reason why hard minimum speeds are so expensive is that the ISP can't oversubscribe at any point. You are reserving that 100Mbps at every upstream ISP. Even during peak times all ISPs can't touch your reserved bandwidth.
https://www.wilhelm-tel.de/privatkundinnen had always excellent latency and peering for me. No problems with stability either, which comes in handy when you're mostly living on another continent :-)
It's an option for those in their own houses, but would hardly help city dwellers. What we need good fiber optic coverage - there is some progress there, but at an inadequate pace.
I did it at home as well. At least 2x more money to pay, but it was worth it because my bread and butter depended on having stable internet connectivity.