You use RE lasers like you use TC SRMs, heat seeking LRMs, dead-fire missiles and flak autocannon shells.
They're niche weapons designed to counter a specific threat, and do so fairly well. However, they suffer agains everything else because of it, and if you try to use them outside of their intended role, you're going to end up with a sub-par weapon system.
RE lasers are not the new "wonder lasers" some people seem to think they should be, and that's great. They also counter some serious threats on the battlefield such as hardened armour pillboxes. It's for this reason that they don't need to be better, they need to be different, and they do that well.
I can guarantee that were they just like standard lasers (weight, size, heat, damage), but ignored F-L and hardened armour, people would be crying OP faster than you could say "I told you so"