I'm iffy on Hyrule Warriors. Particularly after playing through FE Warriors. The core gameplay is fun enough, but leveling up characters gets so fucking grindy after beating the main story, and I don't know if playing it just for the main story is worth it.
FE Warriors did a lot better than Hyrule Warriors in terms of leveling up. Not only do you get more EXP in general in FEW, but you can combine two units and level up two at a time, especially handy for characters you don't like to play as, but will have to use eventually for a restricted mission.
Also, I never encountered any need to grind EXP (read: repeat already cleared missions) in order to beat a new mission, unlike in Hyrule Warriors. In FEW you just keep playing normally and the pieces should fall into place.
But I admit that I loved FEW. I grinded all 32 characters to their max level of 150 eventually and crafted an ultimate weapon for everyone too. The file clocked in at just under 199 hours. I think about 110 hours was what it took to clear all objectives in the game, so almost half of the time on that file went to grinding afterwards, be it levels, materials or enemy kill counts to unlock full weapon strength.
As for your question, I don't think buying Age of Calamity just for the main story will be worth it. Borrowing the game from someone and playing through it, sure. But paying for 8-10 hours of playtime? Nah.