MTG: Arena is a solid program to play MTG on. It's been around for quite a while, and has gone through many improvements, changes, etc.

Pros:

--- Has numerous MTG cards, with multiple prints.

--- Constantly expanding sets to obtain packs from.

--- No money has to be spent to play the game.

--- Occasionally has events to earn monetary rewards, should you get far enough.

Cons:

--- Plenty of items (were and still are) locked behind micro-transactions.

--- Alchemy mechanics as a whole are digital-only (luckily), but are quite broken.

--- It takes a lot of playing to earn gold for packs, way more than it used to.

--- Shuffle system is rigged.

--- Cards are "Graded" by various specs to assist the rigged shuffle system

--- Matchmaking is also rigged. If you win a lot, you'll get opponents that rarely win, and then your entire game will be rigged to let them win.

--- Lack of older card sets, although they have recently added in a few older sets.

--- Rigged matchmaking carries over into events.

MTG: Arena as a whole is a good way to kill time, but a horrible choice if you're wanting more than one or two wins in a single week. The game itself used to be way better years ago, but the more that changes, the worse it gets.  The rigged system used to not be so obvious, but at this point WOTC doesn't seem to care... and that's very sad.

Sidenote: If you're wanting to enjoy MTG digitally with friends, MTG Forge is a community-powered rules engine with zero rigged systems. It also contains every card to ever exist, and nearly all formats.