That description is more or less a correct one.

Conrad von Hötzendorf was indeed after WWI considered a good military commander for quite some time, for example Liddell Hart praised him in his History of the First World War writing that: "His strategy blended the spirit of the artist with the suppleness of an acrobat." and compared him favourably to other WWI military commanders such as Moltke or Joffre. Cyril Falls offers similar comments in his work The First World War.

In German he had several official 'hagiographies', such as Oskar Regele, a former officer of the Imperial and Royal army by the way, and his Feldmarschall Conrad: Auftrag und Erfüllung, 1906–1918 published in 1955. In Germanophone historiography his image started eroding in late 1960s and 1970s when the old guard of the Austrian military historians passed away and was replaced by the younger generation such as Peter Broucek or Manfried Rauchensteiner that was very critical of Conrad.

Comparatively in Anglophone historiography there was little interest in the military history of the Dual Monarchy until 1990s and 2000s with Conrad himself not getting a proper biography until Lawrence Sandhaus' Franz Conrad Von Hotzendorf: Architect of the Apocalypse which came out in 2000 which has a very negative view on Conrad.

A major exception (and more or less the only one) to this was Gunther Rothenberg's Army of Francis Joseph from 1976 in which he offers some major criticism of Conrad and comments on his reputation as well:

"Although Austrian military writers have praised his leadership, and even an English military historian estimated that he was the best strategist in the opening phase of the war, a realistic appraisal does not confirm their judgment." (...)

"Indeed, Conrad, whose capacity for self-deception was to grow under stress, made grave errors." (...)

"On paper Conrad's plans always had an almost Napoleonic sweep, though he often lacked the resolution to carry them out and also forgot that he did not have the instruments to execute them."

Now, why was he considered such a great general if his record was so abysmal?

First off, his reputation before and after WWI - before the war, he brought substantial degree of innovation into the pre-WWI Habsburg army, was popular in the army and his books on infantry tactics were well received which raised both his domestic and international reputation. Moreover after the war he wrote his memoirs (Aus meiner Dienstzeit 1906–1918) in which he Hindenburg/Ludendorff-style denied all the blame for the war, its management and tried to paint himself as a victim; he was supported in this to a degree by the aforementioned duo of Ludendorff and Hindenburg at least partially because it complemented their own stab-in-the-back narrative. He was also still liked by his former colleagues and subordinates who dominated both the interwar and post-WW2 military historiography in Austria, like August Urbański von Ostrymiecz who wrote his biography in 1939 (Conrad von Hötzendorf – Soldat und Mensch) or as I mentioned above Oskar Regele both of whom painted him in a very generous light. Towards the end of his life Conrad also became a proponent of Pan-Germanism and became popular among German nationalists and Nazis, who happily supported and spread his myth after his death.

Secondly as Rothenberg said his plans looked very impressive...on paper. Hence in a pure vacuum these vast and ambitious offensives looked better than they actually were. Moreover as Rothenberg mentioned Conrad was often indecisive.

A good illustration of the problems with Conrad and his plans was the initial stage of the war. Conrad divided the Imperial and Royal Army into 3 echelons - the 'Balkan Minimal Group' (minimalgruppe Balkan) was to be sent against Serbia while Echelon A (A-Staffel) should be moved to Galicia. Echelon B (B-Staffel, comprised entirely of the Imperial and Royal 2nd Army) should be a strategic reserve, if the conflict stays local, it should fight join the fight against Serbia; if not, it should be redirected/redeployed to Galicia together with Echelon A. The plan against the Russians was to encircle them in Russian Poland around Kielce with the help of the Germans and destroy the Russians. There were some complaints about this plan in the General Staff, particularly in its railway office that questioned the logistical feasibility of such plan but Conrad simply ignored them. Now, this would've been a great victory, had the plan worked of course.

Now, when the war broke out and it was clear that Russia will be directly involved in it, Conrad went against his own plans and did not redirect the B Echelon to Galicia, giving it transport priority over Echelon A on the assumption that Serbia stands no chance and would be defeated very quickly and that the logistical infrastructure would be sufficiently swift to redirect troops from the Balkans to Galicia. This was a crucial blunder on Conrad's part that snowballed into more bad decisions.

When it became apparent that the Germans did not intend to support any Habsburg offensives on the eastern front, preffering to focus on France for the moment, Conrad at first hesitated but finally agreed to redeploy the 2nd Army that was already in the Balkans. However the order came late as Oskar Potiorek, the commander of the Balkan forces, already semi-engaged the 2nd Army. Because of that and logistical issues, only cca. half of it was available in time to join the fight in Galicia. This was the worst of both worlds, as their departure both threw a wrench into the Serbian campaign and at the same time a substantial number of troops arrived late to Galicia to make a difference.

Moreover, Conrad decided to go on the offensive without the 2nd Army even being in place as his troops were in danger of being enveloped by the Russians.

What this meant in practice was that the Imperial and Royal forces in Galicia were in August and September 1914 heavily outnumbered having only 34 divisions available while the Russians had 52, instead of the intended flanking manuever they fought a full frontal assault in which they stood no chance against the numerically superior Russians and were pushed out of Galicia while suffering horrible losses.

Sources:

BROUCEK, Peter, Der Nachlaß Feldmarschall Conrad und das Kriegsarchiv, 1975

BROUCEK, Peter, Geschichte der österreichischen Militärhistoriographie, 2000

FALLS, Cyril, The First World War, 1960

LIDDEL HART, Basil, History of the First World War, 1935

RAUCHENSTEINER, Manfried, The First World War and the End of the Habsburg Monarchy, 1914-1918, 2014

REGELE, Oskar, Feldmarschall Conrad: Auftrag und Erfüllung, 1906–1918, 1955

ROTHENBERG, Gunther, Army of Francis Joseph, 1976

SANDHAUS, Lawrence, Franz Conrad Von Hotzendorf: Architect of the Apocalypse, 2000

URBAŃSKI VON OSTRYMIECZ, August, Conrad von Hötzendorf – Soldat und Mensch, 1939