Does CCC 2291 imply smoking is sinful?

Three problems with CCC 2291 you refer to:

1. In the Latin official document, it says "stupfying medications," NOT "drugs" in the sense of all drugs other than alcohol or tobacco. Stupifying medications is an actual class of drugs including Opiates, Barbiturates, Ketamine, etc. and only overdose levels of some hallucinogens. That is a medical standard universally agreed upon, and will certainly be agreed to by every single doctor in Rome. This very clearly does NOT include things like Cannabis, Coffee, Tea, Ephedra species, Coca/Cocaine, etc. No way. Not even close.

2. No previous magisterial / papal teaching addresses this issue at all. There is no Sacred Tradition surrounding the matter. So what is the basis for including such a teaching? To please uptight western semi-modernists masquerading as conservatives by virtue signalling on conservative pet issues like drug prohibition? (Traditional Catholics would say to leave that to the Protestants who invented it. It ain't Catholic).

3. No recognition of there being a difference in the effect of drugs at dosages of X, 2X, 3X, 4X, etc. Consider the case of Kratom, a benign stimulant and pain reliever at low and moderate dosages, but beginning to be a little stupifying at very high dosages.

So is Kratom a "drug" or not? (So go back to point 1).

According to this nonsensical and very un-Catholic interpretation, that depends on how much one takes. What an absurd concept.

Is drug abuse sinful? Yes!
Is all moderate use of them as creature comforts abuse? NO!

Bottom line: no, smoking is not sinful. It isn't even covered in CCC 2291, while CCC 2290 covers it directly.

avoid every kind of excess

The Church doesn't anywhere define just exactly what drugs in the phrase "the use of drugs" means. That shouldn't prevent us from drawing reasonable conclusions about what it might mean, or whether it means something in particular at all.

The first edition of the current Catechism of the Catholic Church was published in French in 1992. In French, the text of interest is "L’usage de la drogue", which seems to mean "the usage of drugs"; but no specific definition of "la drogue" in this context is given.

Finally, the Latin text, which is normative, reads:

Stupefactivorum medicamentorum usus gravissimas infligit valetudini et vitae humanae destructiones.

[The use of narcotic medications inflicts grave destruction on health and human life.–my translation]

It seems unlikely, given (for example) this table of contents for a pastoral document dealing with drugs and addiction, that the Church is concerned solely or even primarily with narcotic drugs in the technical sense; but we're given no further guidance in the Catechism.

The Catechism of the Catholic Church, the first universal catechism in over 400 years, is what is technically known as a major catechism—a catechism primarily intended for use as a reference by pastors and catechists, rather than for use directly by learners of the faith. It is addressed to the bishops and other teachers; when there is a question of what something means, one ought surely to ask, "What would it mean to them?" Given that this is not a technical (theological/religious) word, it appears most reasonable to believe that it is intended to be interpreted (as are most words in the catechism) in the "everyday English" sense; that is, it's intended to mean what "most people" mean by the word.

Taking that approach, it's clear that tobacco is not in everyday usage in most English-speaking countries treated as a drug—that is, treated the same way that for example heroin, methamphetamine, or cocaine are. It's certainly not produced or trafficked clandestinely (for the most part). Thus, it appears that the Catechism is not intending to mark out tobacco as "a drug" except to the extent that this is a typical understanding in society. And given that most Western societies don't view tobacco usage the same way they view the usage of some of these more serious drugs, it appears that the use, without abuse, of tobacco is not prescriptively considered gravely contrary to the moral law and thus not automatically "grave matter", the potential subject of mortal sin.

I've answered your question about masturbation in the linked question.