Unfortunately I have been in the same boat. I had an old community which started in 1999. Started with BBForum software, then migrated to Vbulletin till it became too big to upgrade in a timely matter.
The Discourse team was incredible in their help of converting the forum from Vbulletin to Discourse. But once running, older forum users easily got annoyed, despite us pointing out the useful features of the software.
Even worse, revenue declined terribly, only 30% of ad revenue was left after the migration.
For a new community I would not hesitate to use Discourse, for an old community you should carefully consider whether Discourse would be a good fit.
Many people simply don’t like change and a forum is just a hobby for them, so they don’t want to spent much energy on learning new things. Others will embrace Discourse and never switch to anything else.