Sorry man for you, my RUT240 works well and download speed is fast as 4g capable bandwidht on my site located at high elevated point 1.800 m.s.o.
Singal strenght is one os most important factor to get full dl/ul speds. But not only this, some important consideration to do with alignment to base station and how many "bands" modem can lock when connected to. LTE network.
LTE can provide more than then bands of frequencyes, but this not mean the modem grant all, to reach full ul/dl speed, this in other hands mean be many "variabile factors impact on overall performance.
So my RUT240 is connected at 51/59 dBm with double directive lte antennas, trought 10mt of antenna cable, works like an ftth link, :D but if singal is over to 70 dBm you can get in performance trouble.
Second point you do know, related RUT240 hardware base and cpu power, looks at dmesg print:
[ 0.000000] CPU0 revision is: 00019374 (MIPS 24Kc)
[ 0.000000] SoC: Atheros AR9330 rev 1
This hardware is around on market since 2006 and mips 24k cpu runs a 400 mhz is single core single tread architeture, so for provide faster performance at all is indeed advice to do some additional "tuning" on configuration.
I see slow response when RUT240 loaded with many threads like open multiple WEB UI instances into browser, with 6-7 pages opened RUT is not happy :D I mean you could disable ALL unwanted feature and clean ALL unwanted connections for reach maximum performance capability.
Or of course you can buy some more powerful product if you need handle many parallel tasks/clients connected and high rate internet traffic up to it.
For my experience to this product works well for me and my single DVR client connected to, but I do some litte "cleaning" on firewall configuration for unleash cpu tasks load, this is the truth.
A side note for firewall configuration of RUT240, I check it is full of "many" zones leave alone un-configured and maybe you dont'want some type of advanced stuffs like GRE SSTP PPPTP L2TP, so you can edit "/etc/config/firewall" and clean up unwanted zones/rules with reasonable safety.
If you don't is enough "nerd" to do this , so I can try to clean your firewall configuration if you want, send me a P.M.
Regards