yes it requires moving your money into an address that locks the funds up. (as you say deposit) and also the same when you want to get funds out of LN (you would call it withdrawal so to use LN is 2 onchain transactions.

the "benefit" is supposedly that if you know you are going to pay a certain amount of people X times and you know they use LN. then instead of paying them X times directly with bitcoin. you can save x-2 of costs by using LN

yes the bitcoin fee's have been controversial for about 4 years now. its gone beyond a penny per tranaction which has pretty much rulled out a few third world countries wanting to use bitcoin because bitcoins fees are more than an hours wage in some countries.
before 2014 bitcoin actually had a fee mechanism that actually helped control how much people paid and also it went DOWN when the bitcoin price went up to ensure that when bitcoin went from $6 to $600 the fee in sats went down to keep prices below a cent

..
anyway back to LN
LN is not a bitcoin feature. LN is its own network. a payment system with no currency. in the future LN nodes can use it for many currencies as long as the two users of a channel agree on what transaction format(currency) they will play with.

with that said. if bitcoin continues to raise the bitcoin fee. people will while inside LN prefer to swap btc for a altcoin with cheaper onchain fee's but still able to access the same merchant tools and exchanges. thus there are negatives of LN about becoming a fortknox. people deposit btc and withdraw, for instance litecoin.

as for the whole 'bitcoin fee war', 'bitcoin cant scale'. those 2 things are untrue. fee's can be reduced with code and bitcoin can scale onchain with code. but certain developers prefer to reduce bitcoin from being:
medium of exchange
store of value
payment system

by refusing to code solutions for onchain innovation, to make bitcoin just be:
store of value.
however by removing bitcoins utility of medium and payment. its 'perceptual value' and desirability dies and so that kills the store of value aspect.

its just a real shame that its a few bitcoin devs themselves that are behind the "it cant scale so we wont try" mindset.

LN could have some niche for those who do many transactions an hour. such as gamblers and day traders who arbitrage. but for normal common peoples usage where they only do an average of (visa stat 40tx a month) (btc stat 5tx a month) its harder to preplan spending habits to want to deposit more than 2 days visa spending or 3weeks btc spending to then lock that amount into LN and use it efficiently

but yea even with a niche for 'spam'(repeat spenders above the norm) users, LN still has some flaws and also less security, less ethics and less of the ethos/point of why bitcoin was revolutionary. but as i said LN is not a bitcoin feature. its, its own network which many coins will use. which in itself will not help bitcoin if bitcoin devs continue to not progress bitcoin and instead aim everything in LN's direction as the solution