I started playing Disgaea 1 for my Discord server's game of the month. I bounced off of this game all the way back at release. Now, I've given it a fair shake and it's already feeling like another one of those I would actually have liked back in the day. My experience with this genre is still pretty limited; I've played Final Fantasy Tactics and Tactics Ogre: LUCT along with a couple of the newer Fire Emblem games.
What do you think are the must-play strategy JRPGs?
My experience with tactical RPGs is also pretty limited, but I remember watching a playthrough of Vandal Hearts some years ago and thinking that some of the combat scenarios it presented were rather interesting. I've forgotten more-or-less the entire plot at this point, but still remember those encounters. Not sure I'd put that as a "must play" exactly -- I never did -- but it's worth taking a look at, at least, if you're interested in game design.
Valkyria Chronicles was also pretty interesting. I watched a playthrough of that as well as playing about half of it myself afterwards. It's got an unusual mix of real time control when moving characters around the map, time paused aiming, and other mechanics. If you haven't seen it already, that one is definitely worth checking out.
Oh, I forgot about Valkyria Chronicles! I have a tendency to just randomly pick up games Hitoshi Sakimoto has scored. I didn't finish it though. I think it's fairly popular?