In this study, we propose a novel enhanced deep learning method for the detection and classification of brain tumours known as the reduced complexity spatial fusion CNN (RCSF-CNN) method. This approach integrates complexity feature extraction, which improves the quality of feature extraction from brain tumour pictures. To capture crucial detection properties, image variables such as mean, standard deviation, entropy, variance, smoothness, energy, contrast, and correlation are extracted. These attributes are then employed by the RCSF-CNN to detect and categorise brain cancers. When paired with the discrete orthogonal stockwell transform (DOST) as an intermediary stage, the suggested method illustrates the effectiveness and superiority of the augmented deep learning methodology for brain cancer identification. The studies were carried out using the BRATS dataset via Kaggle, with the network trained on 32 samples and the features of five sample pictures assessed. The RCSF-CNN stands out for its efficient architecture, which includes spatial fusion as well as a critical normalisation step. The addition of class activation mapping (CAM) increases transparency and interpretability, highlighting the model's innovation. The MATLAB simulation tool was used for implementation, and the experimental investigations were carried out on the free-source brain tumor image segmentation benchmark (BRATS) dataset. The results obtained in brain tumour identification reveal an entropy value of 0.008, an energy value of 0.8155, and a contrast value of 0.354. These entropy, contrast, and energy values are critical in the detection of brain tumors. Furthermore, in terms of accuracy, specificity, and sensitivity, the new technique beats earlier methods such as conventional CNN, deep learning with modified local binary patterns, and ML algorithms such as SVM in brain Tumour detection. The achieved accuracy of 98.99% indicates a high level of total correct classifications. The specificity of 99.76% illustrates the methodology's capacity to correctly identify non-tumor regions, while the sensitivity of 98.43% demonstrates its ability to correctly detect cancer locations.