“Timed out too many games in last 90 days”

It completely depends on how many completed games vesus timeouts you have in the last 90 days. In any given day some game move out of that window and some are added.

I didn't join for some time and now I can't join a Christmas Tournament. THIS IS RIDICULOUS.

You have timed out on all your daily games. If you play a few completely, you can easily drop the value.

Though I think in a couple of days it should be 0% as that value is based on games in the last 90 days

Tournament Director can change the Max Timeout setting from 10% to a higher number. I just made it 100% and got someone in.

Imagine I play quickly and another player uses the full time (1 day? 3 days?) per move. We each have a common opponent. I score 1.5/2 against the common opponent. But then that player times out. So now the slow player, who may have had a losing position in both games, gets 2/2. This rewards slow players, who cause tournaments to drag on, in many cases more than a year.
So players who tend to time out are toxic to tournaments: they distort the results and provide incentive for slow play. Nobody forces anyone to play daily games -- play live if you want where there's a clock. But if you play daily games make sure you are able to fulfill the commitment.