Can my British spouse only visit the EU for 90 days every 180 days now?

If you are an EU citizen, then your British spouse gets EU rights through you, because they are your family member. Therefore your spouse is not limited to the 90 days per 180 days rule, as long as they are accompanying you when travelling in order to live in an EU member state. 


See https://www.the3million.org.uk/travel-to-the-eu


When it comes to travelling with an EU spouse for more than 90 days without the intention to exercise treaty rights to live in an EU member state, this is a more complex question - see this question/answer from Your Europe Advice, and this article by Spanish Citizens Advice: https://www.citizensadvice.org.es/schengen-90-days-in-180-day-ruling-for-non-eu-spouses-of-eu-citizens/ .