The IEEE 802.11ax standard, known as Wi-Fi 6, employs a centralized, multiuser, uplink Orthogonal Frequency Division Multiple Access (OFDMA)-based Random Access (UORA) mechanism to improve user efficiency and network capacity in dense environments. In Wi-Fi 6, UORA functions as a contention-based access mechanism within the Medium Access Control (MAC) layer, enabling multiple users to transmit simultaneously over shared Resource Units (RUs) in the OFDMA-enabled spectrum. However, the UORA’s random access behavior can lead to increased channel collisions and low spectrum utilization in dense user scenarios. To address these challenges, we propose a Heuristic OFDMA Back-Off (HOBO-UORA) mechanism in Wi-Fi 6 networks. The proposed HOBO-UORA approach leverages configured spectrum bandwidth or RUs to implement global control over the OFDMA Back-Off procedure. The proposed scheme implements an Additive Increase/Additive Decrease (AI/AD) mechanism to dynamically optimize UORA channel efficiency by reducing idle RUs in sparse networks and minimizing collision probability in highly dense environments. Detailed simulation results demonstrate that HOBO-UORA significantly improves Wi-Fi 6 network performance, achieving a 27% throughput increase and an 18% spectrum efficiency gain compared to standard UORA solutions. HOBO-UORA adds minimal overhead—just < 2% computational at the AP and 0.006% spectral in Wi Fi 6 networks.