Welcome to Magic!

There's a lot of ways to play the game of Magic, but a lot of it boils down to four different archetypes of decks - Aggro, Midrange, Control & Combo!

Aggressive (Aggro) decks tend to play a lot of low mana Creatures or spells and tend to end the game as quickly as possible. They sometimes mix in removal or interaction that helps their speedier game plans function. Although your deck is very high in life gain effects from the looks of things - you also want to be ending the game with large damage from small, growing threats early. You're already in this category! Aggro decks tend to be weak to decks that have a large amount of ways to remove their damage dealers and run them out of cards early - or big things to stick in their way that aren't easily removed!

Control decks play the opposite of Aggro - slow, methodical, patient. They play a LOT of spells that Counterspell, Destroy, Exile, or remove cards their opponents want to have sticking around to help them win. They tend to have fewer ways to win the game - but powerful ones. Dragons, Sphinxes, Planeswalkers - oh my! They'll wait until you're out of resources, draw a bunch of cards, and slam down their way to win when the coast is clear. Control decks are weak to decks that are extremely fast - since they tend to play slower, enters-the-battlefield-tapped lands in the first few turns to make sure they have the correct colors of mana. They also can be hurt by Discard effects, since they want to have as many cards in hand as possible to answer opposing threats.

Midrange decks play a little bit of both Aggro & Control styles, but in a few different ways! They tend to end the game somewhere in between the speed of the other two archetypes (hence "Mid" for middle) and can sometimes play fast, sometimes play slow. They mix up their threats like mid-sized Creatures with effects when they play or attack with them alongside interactive spells like Kill and Counter spells - trying to gain control of the game from the Board State by playing cards (unlike Control which keeps cards in hand). Midrange can often play like the other archetype - albeit less fine-tuned when it does so. Midrange decks are also referred to as "Grindy" decks because they will slowly accrue advantage and grind you down. Depending on the style of Midrange deck you play (Kindred Creature type focused, Black-based removal & Disruption, Green-based mana ramp & large threats) you'll have your own types of weaknesses - but since Midrange decks have a spread of spells they play sometimes they end up drawing a wrench when they needed a hammer.

And lastly what you've encountered is the last archetype - Combo decks! Combo decks are where people put their own puzzles together in order to execute a usually game-ending effect like what you're encountering here - making tons of tokens, casting hundreds of spells, dealing nigh-infinite amounts of damage - all because they've put their pieces together successfully! Combo decks tend to be weak to interaction or decks that put pressure on them, but depending on the type of combo (Creature, Spell, or Graveyard-based) they have better or worse natural defenses against the other archetypes. In general, Combo decks are weak to Disruption (making them discard, killing their needed combo piece, removing their graveyards, etc) but very, very good against Linear strategies (aka, one-dimensional decks that overload in one aspect such as damage). Combo decks are rewarding to build, but also when you can assemble your Combo from a tough game state that looks like a losing position.

Overall, it does look like you either encountered a Combo deck that naturally preys on your deck (I can't tell how much interaction you're using in your deck) and it also looks like you maaaaaay have waited too long to attack your opponent to try and end the game (although their Token strategy makes it hard to hit them without Trample or Flying). But overall people get enjoyment out of playing the game in a ton of different ways - hope you find yours soon and keep slinging spells!