Probably
Your router is older than your phone. Replace it.
Wi-Fi standards have moved. A 2017 router (Wi-Fi 5 / 802.11ac, single-band) physically cannot hand out the speeds your modern devices expect, no matter what your internet plan is. ISP-provided routers from 5+ years ago are usually the worst offenders.
Try this first · Free
Reboot the router
Seriously — uptime over 90 days is correlated with degraded performance on consumer firmware. Unplug for 30 seconds, plug back in.
If that doesn't fix it
Replace it with a Wi-Fi 6 router
A $120 Wi-Fi 6 router (TP-Link Archer AX55 tier) will outperform almost any 2018-era ISP rental. You'll also stop paying the $14/mo equipment fee.
Fiber? No
Solve the router first — you may find your existing plan is already fast enough.