I'm a lifelong JRPG fan who's played just about every 16 and 32 bit RPG there is. Massive fan of anything Square, can tell you just about anything about the first 12 Final Fantasy games, etc. I've even beaten some really obscure shit like Paladin's Quest. But one series I never played was SMT.
First off, the only way to play almost all of the games in English is fan translations, and I tend to shy away from that sort of thing because they're often crappy. So if there are any really good translations out there, that'd help.
Second, they had a reputation for being grindy. I can handle a certain amount of grinding. Dragon Quest games are about where my limit is. I like DQ for the most part, but I don't like walking back and forth just outside of town, mindlessly mashing "A" for hours, and most of them devolve into just that around the halfway mark. I haven't played anything newer than 5 though, so that may have changed over time. Basically, if SMT is any less grindy than the early DQ games, I'm good to go.
Third, I don't really know where to start. I've got forty years of content to sift through. Do I play the DDS games? Do they hold up? I'd be playing the SNES remakes, almost certainly. How about the side games like Nine and If?
Oh, and for what it's worth, I didn't like Persona 4 at all. The level design was insanely bland (nothing but identical hallways) and the battles were too easy. But I've heard P4 is the least SMT-like of the Persona games, so that might not be a problem.
I personally say go for it. SMT 3 Nocturne is a smash hit. It isn't too grindy, but it will punish you of you don't pay attention to weaknesses, buffs and debuffs. The remake is available on multiple platforms.
Other than that the 4th installment was fun and had replayability built into it via its morale system and carrying over your progress if you so choose, but I don't know of you can play it other than on the 3DS.
I haven't played the 5th on the switch yet, but I plan on it eventually.
I've played the older ones before, but if you didn't like the hallways of P4 you probably won't like these either. They're a 1st person perspective so everything feels like a hallway trek.
I've kind of got a love-hate thing going on there. I don't mind first person labyrinth treks because that's the name of the game. It's like when you eat a bowl of Cheerios, you're not really expecting a flavor explosion. Sometimes you just want something bland and wholesome. Persona 4, however, tries to be cool and up to date, but then has the shittiest dungeon design I've ever seen. So it kind of feels like, if I wanted to play Shining in the Darkness, I'd play Shining in the Darkness.
The only thing that bothers me when it comes to very old games with first person labyrinth-style dungeon crawling is a lack of any sort of map. It's why I could never get into Phantasy Star. If I have to get out a piece of paper and draw the map, I'm not interested. And yes, I could just look up a map on GameFAQs or something, but I feel like that takes away the fun of exploring. Automaps are a must. Or something akin to Etrian Odyssey, which I also enjoy. I just don't want to bust out the three ring binder when I want to play a game.