I'm saying the irrationality is in how they built their military and at least a significant part of their intelligence apparatus in a self-defeating way.
On top of that, they further goofed by not rapidly shifting their war objectives to securing Donetsk and Luhansk, then declaring victory and ending the war. If they hadn't insisted on taking Kherson, on fighting Mariupol down to the bitter end, etc, and focused on those two areas when it was clear that their military wasn't remotely capable of what they thought it was, they probably could have ended the fighting in weeks.
Call it job done, claim you were only ever there to secure the DNR and LNR from Ukrainian 'aggression,' and you can present a lesser fait accompli before the international community has largely hardened against you.
Further, they've continuously failed to address the systemic structural problems in the Russian military. They still have the culture of lying, they still repeatedly commit to wasteful and stupid attacks because they can't tell each other the truth, etc, etc.
There are multiple levels at which Russia is still acting irrationally.
Eh, this more seems to me more failures and constraints, rather than irrationality.
They seemed like they were trying to build up a modern army, that didn't really work out as they hoped, and had to revert to a management style that they could do. Lightning offensive operations are always rather risky, and they rolled wrong here.
Taking Kiev brings a rapid end to the war. Grinding forward on Donestsk and Luhansk does not: it gives you the same situation they had for 8 years prior, but with more casualties. If a big part of the goal is securing Crimea, Kerson and maripol are clear and obvious targets: Kerson remember was taken basically without a fight, not taking it would have been a stupid plan, and taking Mariupol would be critical to practically securing Crimea, securing the right flank of Crimea's water supply.
It would seem irrational to not try for a war winning move instead of a slow attritional grindfest if you think it could work, and Kerson and Mariupol were the two great successes of the initial invasion: if anything those should have been focused on more (though its hard to see at this point how much the northern attacks cost vs gained).
Doubling down on Donestsk and Luhansk seems the least rational place, because your focusing on the most heavily fortified part of the front, and where taking ground doesn't really bring you much closer to victory: the only way for example Bakmut as the current fight is bringing victory closer for Russia is to the degree to which its inflicting attrition on Ukrainian forces, which seems to be the current strategy more or less from a lack of ability to do anything else.
Your plan to me sounds less good than the one they actually implemented. Mixed with complaints that the Russians aren't perfect angels. The Russian army is going to have a bunch of drunk corrupt people, because Russian society is full of drunk and corrupt people. The irrational thing is to build a military built on the assumption that it won't be manned by Russians, which may be part of the initial failure (combined with traditional Russian hubris which can get them in trouble). Ideally they would have adapted faster, but, well, institutional issues. The US can take quite a while too to come to major consensus on major operational changes.
But, the fact that we come to different conclusions on the optimal start of the war, and what the Russian military could reasonably be expected to achieve, does not make me think your irrational. Thus my general warryness of applying such a word. It generally doesn't fit.