Do we? We saw it took Maul some time to even pull a lightsaber back into his hand after that. It'll take some time to reach peak power again - perhaps months.
It's not just Maul's legs. It's everything. He hasn't fought in 12-some years. He's obviously not going to be as refined as he was when he fought Jinn and Kenobi. Back then, he was training and practicing brutally under Sidious. It's just a massive difference. It's going to take Maul time to get back into the groove, especially considering he's now unstable and has those legs which prevent him from doing a lot of what he could do before.