TL;DR: Despite being openly 'inspired' by the classic HoMaM-games, it's got worse presentation, worse gameplay, and less content. Just grab Heroes of Might and Magic II or III off GOG instead. If you're gonna style yourself as a 'spiritual successor', try not to be a crappier version of your inspiration...
The long version: I tried to like this game, I really did! But, after hours of playing it, I was having to FORCE myself to keep going, and I couldn't really understand why. Then I watched a retrospective of the old HoMaM-games - specifically I to IV, the entries from before Ubisoft bought up the franchise, which is what Songs of Conquest was self-admittedly based on, and it all clicked. So, let's sort it into three quick categories...
PRESENTATION
Songs of Conquest utilizes a 'retro pixelart' style, which is an immediate point against it since that's the very essence of 'faux-nostalgia'. No games ever looked like that back then - back when those kinds of pixelated looks were common, they were also shown on CRT monitors and TV's, which softened the edges and just basically made it look much nicer. What you're imitating with this kind of 'art' is the experience of playing an old game on an emulator decades after the fact... and HoMaM isn't even one of those games, having always used hand-drawn sprites instead. Thus, while the visual representation compares favorably to King's Bounty - the 1990 predecessor of HoMaM, which was considered primitive for its era - it looks UGLIER than the beautiful, high-contrast, hand-drawn sprites of the ORIGINAL HoMaM, never mind the second or third entry. (Fourth, well, that's a matter of taste.) On top of that, the game also eschews the hand-drawn town vistas from HoMaM in favor of just letting you build stuff directly on the game map, removing one more opportunity to actually LOOK GOOD. And as for the music... well, I wouldn't normally blame someone for failing to live up to the legacy of Paul Romero, the LEGENDARY composer who created the soundtrack of the first four HoMaM games, the fact that this game is called SONGS of Conquest makes it feel like kind of a letdown that the music is just... kind of THERE. It's not BAD, it's just... fine, I guess? Hanging around in the background without making much of itself. Meanwhile, back in HoMaM III, you'd be listening to an opera-performance that made even the mundane act of building a tavern in one of your cities seem epic!
GAMEPLAY
Those who played all four of the original Heroes-titles will remember that the complexity of the game peaked with III, and dropped down a bit with IV. Granted, the behind-the-scenes headaches the company was suffering at the time might have contributed to this, but there's also a good game-design reason for it - complexity is a double-edged sword, and a fine line to walk at times. You need the game to be complex enough to be engaging, mentally stimulating, and challenging - but not so much that it starts feeling drawn-out or turns into a slog. Songs of Conquest is on the 'turns into a slog' side of that equation, easily, since it looked at HoMaM3's core gameplay-systems and went "Hold my beer while I overcomplicate the HECK outta this thing!" So now you've got variously-sized settlements with varying numbers of varyingly-sized building-slots, and five different mana-bars for your heroes, the rate of growth for which depends on your unit composition, and more skills, and more units for each faction! (The peak for Old HoMaM was 7 per faction. Songs of Conquest literally one-ups it with 8. It honestly feels DELIBERATE.) Is it too hard to figure out? Heck no! Is it FUN to keep track of all that? Also heck no! I'm usually all for complexity in games, but so many parts of this package feels complicated just for the SAKE of being complicated. This, then, is made even worse by the aforementioned lack of Paul Romero. Building up your cities and arranging your armies could be kind of a drag in the HoMaMs of old, too, but that music went a long way towards making that slog feel ENJOYABLE. Without that, you're just left with a steadily-growing list of tiresome logistical tasks to undertake each turn...
CONTENT
HoMaM1 - or, rather, 'Heroes of Might and Magic: A Strategic Quest', as it was called before it became a series - had four factions to play as, and no proper campaign. Songs of Conquest compares favorably to that. Compare it to ANY of the other three, and it really, really doesn't. HoMaMII featured 6 factions and 2 lengthy campaigns (Good and Evil, each encompassing three of the six factions) with branching paths along the way. Songs of Conquest - in its base form - has four factions, each of whom have a short, 4-scenario campaign. But what about the DLC? Each adds a whole new faction! Aaaaaand that's about it. No campaign for them. You can play them in scenario- or challenge-mode, that's it. Even at its WORST, during the Ubisoft-days, HoMaM never added factions without giving them something to DO. These DLC campaigns weren't always very GOOD, and I suppose there's an argument to be made about whether bad content is actually better than no content, but these devs didn't even TRY.
So, yeah. You can get the classic HoMaM-games for a SONG, hah hah, and if you haven't played 'em in a couple of decades, they'll probably be more fun to revisit than this attempt to recreate the magic of those games without being able to draw, write, or compose...