Modified from an earlier answer of mine

The Kriegsmarine did plan for a more balanced fleet than the one they went to war with in September 1939. Both the Munich Crisis and the wider climate of rearmament pushed Kriegsmarine chief to plan for a wider fleet expansion in 1938. Commander Hellmuth Heye, a staff officer in the operations division of the Naval War Staff, produced a memorandum in August 1938 outlining an expansion of the navy. Heye's memorandum, with significant additions from Admiral Rolf Carls, later became known as the Z-Plan. While Heye's plan was quite balanced, Carls' additions added an element of grandiose Weltmacht expansion to it.

The Z-plan called for a structured naval expansion taking place over the course of ten years. By 1948, the plan was that the Kriegsmarine would have at its disposal a strong battle fleet with a core of Bismarck-class and H-class battleships, along with more pocket-battleships, and eight carriers. This ambitious program built on preexisting designs, information gleaned from naval attaches, and Germany's own experiments. Additionally, give and take with Hitler over naval procurement meant that the Z-plan was always in a state of flux over its composition as the Führer favored large capital ships but both he and the Economics Ministry balked at having to devote resources necessary for this construction.

Germany's carrier program under the Z-plan anticipated 2 Graf Zeppelin-class carriers and 2 of the Type-B follow-up class. The lead ship of the Graf Zeppelin-class had been laid in 1936 and launched in December 1938, but she was not yet complete by the time of the Polish invasion. Graf Zeppelin's ultimate fate became emblematic of much of the Z-plan; she spent most of the war rusting away as the Kriegsmarine shunted resources towards immediate construction of units that could reach the naval war quickly. Material shortcomings, shortages of dockworkers, and the low priority of the Kriegsmarine in the Wehrmacht resource-allocation hierarchy meant that the Kriegsmarine had to prioritize its construction for urgent needs. The naval chiefs did not give up on their plans for a wider program of naval construction, but instead waited for a change in Germany's war fortunes that would have allowed naval construction some slack.

Carriers had two strikes against them in this milieu. Not only was the time devoted for construction quite high, but they served no immediate purpose in the evolving naval war. The Kriegsmarine's inexperience with air operations meant that its planners could envision very little for a German carrier to do in this context. The naval chiefs would periodically revisit the idea of finishing the still-incomplete Graf Zeppelin, but such plans came to naught. For example, the failure of the Tirpitz to intercept convoys PQ 12 and QP 8 in March 1942 prompted Hitler to order the acceleration of Graf Zeppelin's construction a few days later as part of a northern group for operations in the North Sea and Arctic, but nothing came of this initiative. Raeder agreed, but also knew that at best the carrier would be complete in 1943.

The second strike against a wartime Kriegsmarine carrier was pretty elementary: planes. Carrier aircraft often have different requirements (undercarriage, fuselage strengthening, landing equipment, etc.) that add to both complexity and cost of carrier aircraft. Getting funding for procurement of these aircraft was quite difficult in the 1930s, and the presence of a separate air force added more difficulties. In Germany, as in the Italian Regia Marina, the French Navy, and British Royal Navy, the air services saw the presence of a separate naval air arm as a threat to their institutional base and a rival for funding. Independent air services were able to portray themselves at the forefront of modern technology to civilian decision makers and jealously guarded their monopoly on procurement and designs. Of the national navies who had independent air forces, only the RN was able to overcome this institutional friction to produce a healthy naval air arm, and even there it was compromised. Early war RN carrier aircraft were not as advanced as their RAF equivalents, and the service later had to make do with converted land-based aircraft (Fulmar, Sea Hurricane, and Seafire) and lend-lease aircraft. It was only by the later stages of the war that it received purpose-built indigenous carrier aircraft that were cutting edge. Navies that did not have to compete with a separate service like the USN and IJN had a much easier time getting funding via established naval procurement networks.

The plans for Graf Zeppelin's air group illustrated the problems latent in these type of interservice rivalries. Göring was adamant that the carrier's air group would have been composed of Luftwaffe pilots and its planes would be converted Luftwaffe types (the Bf-109T and Ju-87C) which were not really adequate for frontline service in 1941. There was very little attention given in the German aviation industry to a next-generation carrier conversion, let alone purpose-built carrier aircraft. This sorry tale was reflective of Kriegsmarine's strained relationship with the Luftwaffe in the Battle of the Atlantic One of the larger problems of the Kriegsmarine during the war was its poor coordination with the Luftwaffe's coastal units and the relative disinterest of the air service in maritime operations. The FW-200 emerged as a coastal strike/reconnaissance aircraft largely because of local initiative. When the balloon went up in 1939, the Luftwaffe found that it lacked aircraft with suitable range to patrol the North Sea and later the Atlantic. Consequently, Lufthansa's Fw-200 was the only aircraft in Germany's inventory that could meet these requirements. The Japanese had expressed interest in a militarized version of the Fw-200, the Fw-200 B V11, which had a gondola and provision for bombs. Hauptmann Edgar Petersen, an officer of the X.Fliegerkorps (the unit tasked with maritime strike), saw these versions of the Fw-200 when he visited Focke-Wulf in September 1939 to ascertain whether or not civilian aircraft could be used for this role. Kurt Tank showed Petersen the Bs intended for Japan and assured Petersen that production of a militarized Fw-200 could start very quickly. The RLM was relatively ambivalent about impressing the Fw-200 into military service, but there were few other alternatives.

Given these interservice headaches and the lack of any real need for carriers in immediate operations, it is surprising that development of Graf Zeppelin proceeded as long as it did. Getting even converted aircraft for naval service was a chore, so as delays took place in the carrier's construction, it was becoming increasingly clear that it would be a carrier with no planes. Hence carriers had few champions in the Kriegsmarine and carrier development slouched along as a means to keep abreast of naval developments for the postwar period rather than something for immediate use.