Market orders are blocked for long-dated options because these contracts are illiquid. The lack of liquidity means the bid and ask spread is very high, which can have an immediate adverse effect on your profit and loss (P&L). In illiquid long-dated options, the bid/ask price could be at a price far from the last traded price or the theoretical price of the contracts. This wide spread can result in poor execution prices when you use market orders.
You can use a
limit order as a market order
to safely execute this transaction. This gives you better control over the execution price while still allowing you to trade these contracts.