Marriage may be contracted any time of the year. The solemn nuptial blessing only of marriage is forbidden from the first Sunday in Advent to Christmas, inclusively, and from Ash Wednesday to Easter Sunday, inclusively. The bishop may permit marriage in these seasons for a good reason, even with the nuptial blessing, as decided by S. R. C. June 14, 1918, but the parties must refrain form too much pomp.
This would seem to make clear that St. Thomas was discussing discipline, and not doctrine, in that section of the Summa. Unless, of course, the OP thinks the 1917 code is modernist.
I actually did read the entire section on marriages in the Code of Canon Law (1983) and it doesn't mention any prohibition against weddings at specific times of year but it does give respect to local customs. It seems, after a first reading, that the local ordinary has a large say in how the practices are carried out.
My remark to Sigismund was not that I thought he was wrong because even the Angelic Doctor would say that there are always exceptions. Even on the prohibited days of Good Friday and Holy Saturday, exceptions are allowed in the event of someone being on death's door. The exceptions are just that, they are exceptions. My grievance was the tone of insolence that I thought I saw in Sigismund's comment toward the memory of St. Thomas Aquinas.
Funny thing is that yesterday I could not find a Code of Canon Law from 1917 that was in English so I couldn't compare the two. Now that Dolores has done the yeoman's work for us, it is good to know that the changes are that drastic.
The introduction to the new Code of Canon Law made it clear that it was intended to be a new Code for a new Church with a new Ecclesiology. Look to the intro on the Vatican's own website and not to individual code descriptions. The revolutionaries work in broad daylight because in their warped vanity, they fully expect people to not notice. They are right in that regard because the largest group of Catholics in the post-Vatican II world are those who stopped going to Mass altogether and, in my view, this was the most likely reason for the Vatican II changes.
As a form of bullying tactics, the Code of Canon Law (1983) declares null and void all previous Codes whereas Pope St Pius X, having a filiel affection for Holy Church and a love of Our Lord and Our Lady, allowed prior codes to remain standing. It's just like with Pope St Pius V not abrogating all pius liturgy forms that had been in effect for 200 or more years. Compare that to Pope Paul VI who commisioned a group of lapsed Catholics (these are the modernist Catholic theologian), openly heretical Protestants (the famous six that did a selfie with Pope Paul VI) and deceiving Masonics (enemies of the Church) to design a Mass based on the Calvinist service and forcing it upon the entire Latin Church.