Yeah, we don't need to preface every argument with, "it's based on preferences" or stating, "in your opinion". Of course these claims are based on preferences and personal opinion.
Anyway, there's no such thing as a "good" turn-based system. There's little strategy or thought in turn-based games outside of SRPGs which are not JRPGs. Mostly, surviving in a turn-based JRPG is an issue of maintaining buffs, removing status effects and healing party members routinely. I have no idea how anyone can find such repetitive gameplay interesting or fun. And turn-based combat is about as interactive and thrilling as watching flashy paint dry for 50 hours (seeing the same animations over and over). Then there are the designers who make some enemies and bosses so overpowered that grinding becomes a necessity, forcing the player to spend more time with their dull as dirt combat system.
JRPGs will naturally be a step below SRPGs, since they lack or greatly simplify the movement/space factor (or the manual control of it). This is the most elegant and meaningful way to add complexity to a strategy game and is by no coincidence the most defining trait of this whole breed of gaming (even outside videogames, even just visually, e.g., "the grid"). However, what you are saying is flat out idiotic, which is why I'm only replying for other people's sake. What JRPGs have in their favor is that they choose to narrow their focus or use their abstraction to create systems that are, even if they are not ultimately deeper than a simple, good grid-based game like a Fire Emblem, rather unique, novel, or just overall very interesting to play around with. The very best example of this that comes to mind is something like The Last Remnant, where your parties placement in the 3D space is virtually out of your control, but the game instead chooses to focus on "engagements" and "inferences".
Two caveats here though: 1) in theory, most of these mechanics could be adapted to SRPGs to further increase their complexity, and, unsurprisingly, there are JRPGs which do not make a worthwhile attempt at replacing "space" with some other manner of complexity, 2) many do though, but their effort is cut short by an extraneous systems ("leveling" being by far the most detrimental trope in existence) or a simple lack of care put into difficulty to make these systems matter.
For 1), consider that, at the end of the day, SRPGs simply don't end up doing this to a significant enough degree, much like the best macro strategy games are also not doing what the best tactics games do; granted, it's really cool when it does happen, such as when the Devil Survivor series just takes the SMT combat system, smirks and all, and dumps it into a pretty good SRPG (and thus ends up creating arguably the best games in the whole meta-series). So for what it's worth, JRPGs remain an avenue for interesting mechanics, because both genres end up focusing on different things or at least do things differently.
For 2), we have to consider how much the "turn-based battle system" is really at fault for the overall game allowing players to overlevel or a careless approach to difficulty (not to say a game without challenge can said to have to good tactical combat overall), which is to say, there's no reason to believe that a "turn-based system" inherently suffer these problems and we can both imagine and find games which don't - sometimes by measuring to what extent they do, since leveling is so ubiquitous (it's not like SRPGs are any less affected, considering that there are people who see a game guilty of the worst JRPG flaws, Final Fantasy Tactics, as the best SRPG). Your basic description of "in JRPGs, you basically do these four things" is stupid because you "basically" do a handful of things in almost all games. The weight and meaning of your actions, thus the satisfaction you can derive from doing then, depends entirely on the context of the overall system. What kind of thought goes into healing, buffing, etc.? In a general scenario (perhaps, most commonly in a boss fight), what are your options and their consequences (including taking risks based on probabilities)? So it's simply a matter of a game having challenge, or enough challenge, to make your actions count. Something like the SMT series fits the bill often enough, but just as often suffers from a bad difficulty curve. We could think of even better examples, which maybe don't, but I want to stress that a bad difficulty curve (an extremely likely occurrence in all games with free-handed leveling systems, turn-based or not) is a separate issue from a style of combat being inherently flawed - or, hyperbolically, worthless, since apparently there has never been or nor never be a good turn-based combat system lol.
It's worth noting that "grinding being made a necessity" is almost never ever true; this is certainly not the case in games made in the last 20 years. Grinding is almost always nothing more than a fail-safe to catch bad players, a sliding difficulty that, while hurting the game's overall depth, allows everyone to beat the core game. JRPGs have hard bosses you can beat with smarts and good prep; these can be the satisfying fights that make combat systems matter. The issue with grinding is almost never that you have to do it, it's that you are allowed to do it (or you may do it by accident). If anything, it's a pretty sad thing when a player manages to get the impression that they have to grind; if there were no leveling mechanics in the first place, they would just understand "oh, I have to get better", like every other game.
