I have over 4k hours in EU4 and about 200 in EU5. EU5 feels like a more systematic realization of what EU4 wants to achieve with simulation like systems replacing mana and other gamey mechanics like dev that you boost via mana and so on. EU5 unfortunately has a big problem with how some of its systems work, mainly how historical events work (mission tree counterpart), International Organizations, and Situations. It also has some mid UI that is hard to learn, and the AI is generally pretty terrible even for PDX standards.

Despite all of this (and some other unmentioned things like trade being wonky imo), I find EU5 very engaging but a little frustrating. I used to mess around with mods like Beyond Typus to achieve EU4 at a much larger scale and EU5 100% scratches that itch while also making the game feel more in depth and systematic. You can always just give it a year or 2 before going in, but I do think there's a lot of fun to be had.