Job wants to roll out M365 apps, sharepoint without hybrid identities. Am crazy or are they?

Started a new job as M 365 admin. Company wants to roll out M365 apps. Wants me to set up teams policies and eventually migrate them to sharepoint. Also considering intune in the future. They are already using exchange online so there are users in the tenant

However, devices are domain joined and there is no ad to entra sync. Today I suggested setting up ad sync so we can use hybrid identities and not have two sets of creds (cloud apps and on premise). Said it would likely be smoother for us and users. Also suggested syncing devices so they are in a hybrid joined state and they could possibly migrate to intune in the future

Basically they told me they don’t think it can be done and they’ve been told by outside vendors it’s unnecessary and over complicates the environment. I haven’t looked at the on prem AD domain yet but they are telling me UPNs and smtp addresses will not match what’s in Entra. My understanding is they do need to match to convert the entra accounts to synced ones

Apparently some outside vendors managed their exchange instance and migrated them to exchange online and they had like no control over it. I asked if I could take some time to look through their on prem AD and they were also averse to that

Now I’m feeling like what did I get myself into? My main question is, who has the misunderstanding here: me or them? To me setting up the sync doesn’t seem like a big deal, is a prefix to integrating with entra and other cloud services, and will save them headaches.