A lot of tables have loose players who bet and call too much on almost every street. What are the theoretical adjustments to take advantage?

Our value hands will just get more value.

Draws should become more playable, with better immediate and implied odds.

But what about medium strength made hands? It seems that the adjustment must be to call more, but then you become one of the loose callers yourself. Do you just have to accept the variance and call more?

Do semi-bluff raising, or raising weaker value hands for protection have any theoretical place?

Well there are two main types of loose poker player(loose passive and loose aggressive) and then there are extremes based on those two types. When it comes to loose passive players they are going to be open limping/over limping preflop waaay too often. Against these types of players I'd say a good/strong linear preflop raising range is best. You'll be basically printing money against these guys post flop. I'd be value betting a bit thinner than I normally would(also a bit larger than I normally would) as well as folding more often to just about any sign of aggression(obviously depending on my holdings). Long story short is value bet more often and bluff less often.

With loose aggressive players you also want to have a stronger/more linear preflop range and should be 3betting them fairly liberally since their preflop range is wide/weak. This can also greatly depend on what they do when you 3bet them. For example, if the lag is calling almost every 3 bet you really want a strong linear 3bet range whereas if they'll actually fold you can have a little more polarized preflop 3 betting range. Post flop these guys will often cbet at a fairly extreme rate and often will attack any perceived sign of weakness so it can be a money printing situation to check/call, check/call, check raise(obviously depending on the player and position against them). They'll often barrel scare cards too.

In general you should be doing the opposite of what they are doing. If they're calling too often then you shouldn't be calling much. If they're raising too often then you should be calling/3betting more often. What is bad is doing the same thing they're doing. Calling a loose passive player's raises with medium strength hands is a horrible idea but against a loose aggressive player that isn't nearly as bad.

Players who bet too much and players who call too much require different strategies. When players bet too much, you should let them bet. When players call too much, you should bet more. When players call too much when bet into and bet too much when checked to, it becomes a judgment call on which path is more profitable.

The more aggressive a player is, the more often a medium strength hand can be used as a bluff-catcher.

Raising with the second-best made hand to bluff out the best made hand while possibly getting the draw to call is a normal tactic in a game like limit hold em.

lean towards an exploitative style as opposed to GTO

value bet a lot more and condense bluffing range to stations (call too much)

let the aggro bettors hang themselves, so take passive lines to let donkey pull the cart instead of us pushing (bet too much)