The impact of miner revenue structure changes on the altcoin market is complex. As the block reward decreases and miners rely more on transaction fees, it can affect the supply and demand balance of altcoins. Miners may adjust their mining strategies based on the profitability of different altcoins, which can in turn influence the price and market capitalization of these altcoins. Additionally, the overall security and stability of the altcoin network may also be affected if miners reduce their mining activities.