I used to like it, but every consecutive expansion after The Wraith of the Lamb just ruined it more and more. The latest expansion I was looking forward to, but it's just a broken, incomplete mess. I'm sorry, I'm not paying for it to be done X years in the future.
Ironically, Isaac's vast variety of content is what makes it a mess; too many shit items or conditional items clutter the pool and are generally duller and less inspired than the vanilla items, and make most runs dull and uninteresting. Bosses like Delirium or the Witness (Mother) are not fun to play against. Their attacks/mechanics are fun, but it all relies on you having a good run, and less on having good skills. Items/Dice Rooms that ruin the run are just tedious to deal with and not fun at all.
I feel Our Darker Purpose could have been a far more interesting and memorable experience. The core game is just so fun, and all the items feel like they have a purpose and have more impact on the game.
Touhou Endless Dream is another roguelike that just surpasses Isaac 10fold. A good roguelike doesn't need to have 1000s of items and 100 bosses; it needs to nail the core gameplay. TED has many characters that actually play different, and don't offer a simple stat based upgrade or start with a generic item.
Of course you can't go wrong with Enter the Gungeon. EtG kinda showed me what a Rougelike can be and what Isaac should have been. Compared to it, TBOI just seems lazy and uninspired.
Also AAA get a lot of flak for milking the customers for money, but how many Console Rerelease and shitty expansions has Isaac had?