Poldark is the kind of drama that just goes on a little too long and would have been better as a three seasons type of things. Interestingly, the intrigue seem to both stretch, almost becoming boring, although the show spans an incredible amount of time. That is one of Poldark's witness. Despite having such a strong timeline to explore, it seems like it falls back on the same issues, over and over again. At first, it's good drama but then, it just gets tedious. Characters that never seem to evolve and gain perspective although so much time passes. It's a bit of a shame really. Since most characters are actually very charming and you just want to root for them but they do make it hard at times and you're left wondering why you bother...

Watch it for the pretty scenery, the passionate drama. You'll probably stick it to the end by season 3 because you'll have gone that far. Just prepare to lower your expectations as episodes go by.
It's still great acting, lovely characters (mostly), and amazing landscapes. The scenarii are the let down.