This one's a doozy. On one hand it's a competent game in its own right, on the other it's an abysmal sequel.
Storywise:

• Countless references to previous installments which are just pointless fan service: oh look, a guy is called Hubert de Layle IV; oh look, a staff is called Cane of Oracle Millu. It also continues the "proud" tradition established by Disciples 3 of misspelling Solonielle as Soloniel, and started a new one: Yatta Halli instead of Yataa' Halli. She was also a queen guys, not just a hero.
  
• The Empire is almost pure evil, The Elven Alliance are mana addicted insufferable a*sholes... and Legions of the Damned are now honorable. Legions of literal demons from hell. Undead Hordes, who didn't care about anything but serving Mortis, now want freedom since there were Undead before Mortis was even born. So that's a retcon as it contradicts previously established lore of Mortis creating the Undead in the first place. In addition, since Disciples 3 didn't have Mountain Clans (Dwarves) due to lack of budget and the publisher cutting their losses mid development, the developers of Liberation decided to go with it and made them extinct off screen. They even killed off Wotan.
  
• So many retcons. I stopped counting after the 10th one.
  
• The writing is truly schizophrenic. On one hand you have some really good moments between companions, incredible choice and consequence design, on the other a few events, or bits of lore, are so incredibly groan worthy, so contradicting to the original lore, that I was screaming internally. If you do not know the lore of Disciples, you'll get lost in the sea of lingo and references. If you do know the lore, you'll hate the retcons and the direction of the story. Further, the main character and her sidekick are insufferable. There's not a single dialogue in the game that isn't marred by endless quips and jokes. The dialogue is sometimes on the level of Joss Whedon cringe. Yes, that bad.
  
• The main antagonist shows up twice. Once at the mid point, second time at the end. Barely anyone ever speaks about her. When she appeared as the final boss I was like "Oh right, this character exists. And she's the root of all evil? Ok, I guess?".
  
• Romance options with random NPCs are extremely cringy and on the level of what a 12 year old thinks maturity is. On the other hand, companion romances are quite decent. They should just remove all the other options.

Gameplay-wise:

• Companions are carbon copies of high tier units: the same exact abilities, just more powerful.
  
• Slow and tedious progression.
  
• Painfully slow combat. Even at 300% speed you have to:

1. Wait several seconds for all the pre-battle group wide buffs to be applied.
   
2. The game announcing that the battle starts.
   
3. Each time a round is finished, the game announces a next round is starting.
   
4. Each time a unit uses a power, moves, takes a sh*t, or farts, it takes a few seconds for control to return to the player.
   
5. Some units take ages to move, especially dragons. They go through the entire animation of lifting their asses up, slooooowly flying to the destination, and then carefully putting their asses down as if sitting on a cold toilet seat.

Other issues:

• Awful voice acting at times. The Legions no longer speak in ominous Latin. Most of them don't even have a voice modulator. They just sound like regular dudes. The Cultist sounds like Goofy: "hyuk hyuk, I will drink from your skull, hyuk hyuk". Modeus speaks with a stereotypical lisp. It's hilariously bad.
  
• Almost pedestrian art style. Very few creatures are designed well, and those that are, are replicas of Disciples 1 or 2 design. The worst is the Empire's Inquisitor: it's a regular woman with a traffic cone for a helmet on her head and who's wielding two swords. She's also barechested for no reason. She looks like a cheap female Pyramid Head from Silent Hill 2 cosplay. And Death Knights are literal d*ckheads. It's downright horrendous.
  
• Mobile game UI which is unwieldy with minuscule icons in-game yet humongous within the menus, an inelegant amount of submenus, with pointless "hold M1 to do stuff", having to return to the castle to gather your resources which are being produced on a hourly basis, etc. The main menu has social media icons and links in the upper right corner and, after playing a set number of hours, a message asking you to review the game is permanently displayed there.
  
• Disciples Liberation is too long for its own good. It took me around 55 hours to complete my first playthrough. Near the end are 3 boss battles, almost in a row. It's extremely tedious. What's worse, to get the "true" ending, you need to finish a New Game+ mode called Liberation mode. There are some cool features, i.e. you receive 2-3 times more XP thanks to which you easily destroy your enemies as you become overleveled within the first 30 minutes, and new dialogue options allowing you to literally metagame with an in-lore explanation and e.g., uncover a traitor in the very first dialogue with them.

What I do like:

• Characters are generally fairly well written and have their quirks, e.g. Ejamar the Necromancer calling you "dear fiend", Bagthal calling himself "Of Nothing", etc.
  
• Choices and consequences are surprisingly well done. Interconnectivity between quests is actually that of a decent RPG. You can decide to attack and kill almost anyone.
  
• Music is pretty good and has some absolutely fire tracks, e.g. Fury Unleashed, or The Dance of Blades.
  
• Mix and matching units and spells for battles can be addicting, until you eventually get bored of it due to the low combat speed.

As tired as this phrase is: it's a good game, but a bad Disciples game. Passion was put into this title, but it being called "Disciples" is damaging both to it (as people have specific expectations after over a decade since the third game) and the franchise itself (as it takes way too many liberties concerning story and gameplay). It's a soft reboot nobody asked for.