It depends on how many people are in your household. Even with really good traffic shaping, 100mb/s can be a problem if there are 3+ people these days. Game downloads/updates, movies, file transfers, combine that with game consoles moving away from storing data locally, cloud services, real time coms such as ssh/rdp. One person can chew up that bw at times and affect others in the household trying to do voice chat or gaming.
In addition to this, not everyone is doing bbr+fq_codel or cake traffic shaping, so they need the burst overhead capacity. Even those using fq_codel seldom have the right options set. And even then, most consumer routers have low end cpu's and barely any L1/L2 cache. HTB adds a lot of context switching on the router. If you hit the buffer on your cable modem or CMTS, then real time applications get a lot of jitter.
The other issue is the mix of operating systems in the household. Not every OS may be doing fair congestion control or even support/enable ECN. Not every consumer modem supports ECN properly.