No I wouldn’t either, done it plenty of time before, back in the day when azure ad was not an option. It’s definitely doable technically, but it’s a significant amount of work to keep up.
If it’s a medium/large org, e g. 100/200 users and above, it might be worth considering some hybrid solution, in order to not have a bad day when some poor soul at Microsoft had a bad day and their cloud goes away for a few hours due to DNS issues (like we’ve seen before).
The Hybrid of cloud + on prem in this case, I’d be considering would be something like Azure AD(cloud) + AWS or GCP Windows VM (on-prem).
Reason for on-prem bring in a different cloud is because managing your own on-prem windows hardware properly… backups+security+reliable power+fire systems+reliable networking across multiple ISPs for redundancy… IMHO, it’s too much mechanical busy work, even if you can throw windows server into VMs, and migrate it around a couple of run off the mill dell or gigabyte machines, and even if you cut some corners when it comes to your server room … it’s still a lot to deal with for one person.
As an individual admin, I’d maybe consider a local, on-site, AD replica only if
a) there’s a lot of local windows machines or AD clients (e.g. 100+ in one building or in one network)
b) there’s enough resources in the company to support the maintenance
… and even then, I’d think hard re whether these caching DCs can be a pair of easy to throw away, encrypted root Linux boxes running samba, that are trivially rebuildable from Ansible or a docker-compose kind of setup. That way, in theory, if they die, you can just grab and repurpose first PC you have lying, or just show up with a third machine ready to go, and make up for it.
One thing that looks interesting but I (fortunately for me) did not have to look into before, and don’t have personal experience with is Jumpcloud and similar competitors. Them not being Microsoft might make them more open to integrations with various third parties that may be Microsoft competitors.