Well, you don’t ‘need’ a switch, that’s a choice.
But yeah, I have two light groups in my house both of which can be controlled by smart switches if required without issue, because the switch speaks to homeassistant rather than directly to only one of the bulbs. The difference is what the switch controls.
If your switch directly controls one bulb and you change its brightness, then the other bulbs in the group won’t be affected, so your current approach employs an automation to monitor the change and duplicate it.
However, the downside of your current approach is that you can now only control the lights individually in the future if you disable this automation, which adds complexity.
But if your switch controlled the light group in homeassistant instead, then changing the brightness via the switch will automatically apply to all bulbs in the group, but if you want to individually control the bulbs (low powered occupancy simulation whilst you are away, for example) then you can without having to activate and deactivate other parts of the system.
I see it as like a 4 stage fallback system here.
Stage 1 - fully automatic, lights are on when they should be, nobody really needs to touch any switches and 99.99% of the time they never do.
Stage 2 - the 0.01% of the time that the automation system doesn’t suit the situation, simple voice controls to change what you need.
Stage 3 - if you really must use a switch (maybe the internet goes wonky - we use Alexa for voice control), then the smart switch is there, ergonomically positioned so that it’s easy to find and use, controls all the lights you would expect it to.
Stage 4 - total system failure, emergency fall back, revert to the old, hidden hardwired direct switches.
This also applies to my heating system too.
Stage 4 has only happened once in the last 3 years due to hard disk failure, so we spent a couple of hours of an evening in November reverting back to the caveman days, then the next day when the new hard disk arrived popped it in and back to stage 1.
Works well.