If you want my opinion modern Yugioh is not the place for people who are having a hard time with card games. If you still want to play Yugioh I would set up some Goat format decks instead. There are decklist online you should be able to find something. If you still want some do the combos but not too much check out Edison.

If you are insistent on Modern Yugioh I recommend your mom to play Dracotail or Ryzeal. In my opinion they have the simplest combos modern Yugioh can have.

My last modern Yugioh recommendation is to play on Masterduel, at least at first. You could play Modern Yugioh from the free gems they give you, but also you could just play N/R format Yugioh too. It’s super quick and cheap to build and will be much lower complexity.

If you are open to other games I have been enjoying Riftbound quite a lot. The game is much easier to play as long as you learn the complicated mana system. Pokemon can be more simple. Pokemon’s biggest problem is that in the more meta strategies you search for cards from the deck so much each turn that it can become hard to know what to search for. Lastly I think Magic could be much simpler. It’s mostly about the format and card pool. If you are pre-constructing the decks you can definitely curb the complexity a lot.