1. It can be. It really depends how you play. We play casual gaming so we don't really go all out usually on 4 of this card and 4 of that card unless it's a deck we are determined to build for the lawls. Those decks are usually built by people who are into tourneys, which we don't usually go to.
It certainly can be addicting though. I find myself having to be pulled away from the racks at Walmart a lot or I'll end up buying a pack. One side says "It's only a few bucks" and the other side says "that's what you said the last 5 times... this week".
Overall, it depends how you look at it. I know many people who spend $60 a pop on video games every month. There are months I don't spend a quarter of that on cards. MTG also has a much longer playability than video games because it's always evolving depending on what you do with it. It really all depends on you.
2. This is a good thing, though it can seem overwhelming. At current, there are a little over 21,000 cards including tokens and other specialized cards. However, that being said, a lot of the older cards you typically won't use in modern decks unless you're a tourney player using a Power Nine for Vintage play which can cost several thousand dollars.
You don't need all 21,000 cards and more often than not, it's pointless to look much into them. The majority of them are common cards which have either been reprinted in newer core sets or there are new cards with the same effects and abilities. The only time I really look at getting older cards is when I need something specific for a deck, in which case, I use the search engine by the effect I'm looking for since it's pointless trying to memorize all the cards, and buy the singles I need which are usually pretty cheap.
The amount of cards adds a lot of variety to the game. You can make decks that are completely different from other players or tear decks apart to make something new.
3. There are basic rules like in every game. Once you learn the mechanics, you're good to go. No one expects you to know every rule. This is why they have judges at tournaments who do know the rules. This is also why there are websites dedicated to rule searches if there is ever a dispute on the mechanics of a card.
4. Because artifacts add another element to the game. It all comes down to what a card does and how it works as to whether or not it gets used in a specific deck. Many people use artifact based decks, but unless they are built properly, they will fail. More often than not, even a colourless artifact deck has coloured support cards. Remember artifact cards have no instants, sorcery, or enchantment effects unless it's specific to an artifact creature. Not to mention, they generally cost more mana to cast.
It sounds to me like you needed someone better to help introduce you to the game. It can be a little tricky at start, but if you get the right people to help you with those starting blocks, it makes the game so much easier to learn.
The game itself usually remains the same rule wise unless a new type of card is introduced in which case it's usually a single rule rather than a load of new ones. Most recent example would be the double sided flip cards they added in Innistrad... something we are all hoping they never do again from the sheer annoyance these cards are where you flip them over after a specific action is taken.
I think you had a really bad introduction to the game and weren't given the information you probably should have been given to get started which is why you feel overwhelmed. Overall, it's not a very complicated game, but it does take a lot of thought to play it at times. You tend to grow into it after a while. And yes, at first you will be dominated because you need to learn the cards in your deck and what the specific deck does in order to use it correctly. Otherwise it's like trying to use a flat head screw driver in an allen screw. You might get lucky one time, but it will work so much better if you use the right tool.
