https://www.duckware.com/tech/wifi-in-the-us.html
Wifi throughput to a 802.11ac wireless device will likely max out at around 600 Mbps (±60 Mbps) for 2x2 MIMO, to 1000 Mbps (±200 Mbps) for 4x4 MIMO no matter what 4×4 router is used (when right next to the router). And the far majority of ALL wireless devices today (smartphones, tablets, laptops, etc) are still only 2x2 MIMO. So your client device is almost certainly causing slow wifi speeds (and maybe not your existing AP/router).
The weakest link in Wi-Fi is YOUR client device: You have 1 Gbps Internet, and just bought a very expensive AX11000 class router with advertised speeds of up to 11 Gbps, but when you run a speed test from your iPhone XS Max (at a distance of around 32 feet), you only get around 450 Mbps (±45 Mbps). Same for iPad Pro. Same for Samsung Galaxy S8. Same for a laptop computer. Same for most wireless clients. Why? Because that is the speed expected from these (2×2 MIMO) devices! This section explains in great detail exactly why that is. You may safely skip to the next section for a shortcut if this section is too detailed/technical for you.