I used to hate Touchwiz.
It works perfectly fine without Samsung account. I couldn't be bothered to make one, and I'm not missing anything. If you do not have Samsung account, Bixby won't bother you either. Just because there was a step to make one in the OOBE, doesn't mean you have to make one, you can skip it.
Updates are there at the beginning of every month, I have no idea why you think they are slow (and for some reason, S8 updates are there day or two in advance to S10 updates... go figure). Samsung doesn't insist on using cloud services, unlike Google, where Google Photos nag the user to enable upload to cloud, even if the user never intends to do so. Google apps do not know the answer "no", Samsung (or Sony) apps do.
The bixby button is an endless pain, thankfully I found bxaction that helps stop it.
It also has features, that will show in the next Android version. The dark mode, for example, has been there since they introduced Pie version. The only one feature that I noticed they removed, is the SIP client, which most users do not use anyway.
They do ship their keyboard, but you can still choose you own, the Android mechanism for that works. I also do not have any problem with it, it is on par with the Sony one, for example.
What I do appreciate though, is that their software doesn't push me into cloud services. Their gallery is perfectly fine with working just on device, without asking me to upload my photos somewhere, unlike Google Photos, which doesn't know the answer "No, thank you, don't bother me again". Samsung account is entirely optional, I still didn't create mine and it works perfectly well without it.
As the cherry on the top, the esthetic of OneUI is nicer than Google's. It makes somewhat softer impression, where Google apps are unnecessarily harsh.