"nous avons célébré" should surely be in the imperfect since it says before it, it's "like every year"? a recurring action

Question

Accepted Answer

Bonjour James,
Maarten’s explanation for the use of Le Passé Composé instead of L’Imparfait is right.
‘Last weekend’ refers to a specific event and hence the use of Le Passé Composé. L’Imparfait is used for an ongoing action or a recurring action that has not been completed and with no clear time frame
See following links: the-passe-compose-is-mostly-used-where-in-english-we-use-the-simple-past                     
le-passe-compose-usage-on-its-own-or-with-l-imparfait
I hope this is helpful.
Bonne journée !

Answer

The sentence is referring to a specific event “last weekend”, with a ‘by the way’ reference to past years. Passé composé is correct to describe the specific event. It is not a general statement of past, habitual activity, and imparfait would be incorrect here.

Imparfait is difficult for English speakers - suggest looking at multiple good native speakers sites for various ways to describe. Link to one I have found useful but there are many available. Obviously they overlap in explanation but often there is a different approach that can consolidate the concepts.

https://www.frenchtoday.com/blog/french-verb-conjugation/passe-compose-versus-imparfait/